Polsilver long life

...Typically the sharper a blade, the quicker it will lose its edge (this is the same concept in knife sharpening and bevel selection). Obviously the metallurgy plays a part in edge retention as well...

Therein lies the rub. There are for example many "super" steels used for expensive knives that can hold an edge for an unbelievable amount of time in hard usage. The downside:  they are a SOB to sharpen. You need diamond and lots of patience. Many who spend a lot of time in the actual field like an old carbon steel knife as with a few licks on a stone and you're back in the game quickly. 

The things with razor blades for shaving is that what we sense as smoothness is actually sharpness in a bizarre way. These two are not independent of one another. Wilkinson Sword introd a non-coated stainless razor blade for shaving in approx. 1956 -57 and they shave like a bean can lid!!    It was only when they went to Teflon (PTFE) coatings on these in the early 1960's did they become famous. The coating is what prevents "drag" and the platinum and or chrome is the edge hardening that even while underneath the thin PTFE coating (think in angstroms, or millionths of an inch) keeps the edge longer. It's a fascinating balancing act really.

I do 6 3 pass shave a week and generally like to start with a fresh blade on Monday when I have 2 days' growth.  I think I'm tossing blades that probably have more shaves left in them and it pains me to think I've been so wasteful.  When I first started out I would change blades after 2 or 3 shaves but then realized that I could get more out of most blades and I upped it to 6.  I rarely encounter blades that can't seem to give more than 2 or 3 quality shaves but it does happen - I won't mention the brands for fear of triggering outrage

My go to blades right now are the Feather , Polsilver SI, Kai, Israeli Reds and the other Personna that comes in the plastic container with the blue and red on the label.  Those ones have neat print on the blade.  I have a box of Personna that have the messy print on the blade and those aren't so great.

The phenomenon of sharp blades dulling quicker isn't noticeable to me in practice.  Feather blades just do a good job of slicing off those whiskers.  If I use a blade like say the Vikings Sword, which are a nice comfortable blade, I find that in the difficult areas of my beard around my chin and lip where the whiskers are much coarser, I end up going over and over the same spots getting the sound and feel of whiskers being removed without whiskers actually being removed.  The blade is just scraping over them without cutting them.  That leads to irritation on two levels so despite liking some of those "comfortable" blades, the sharper blades give me the better shaves even after a week of use.

I'm rotating between Feathers and Polsilver Super Iridiums. The Feathers go in my Feather razor and give me nine passes before I start noticing some drag and tugging. The Polsilvers go in my Rockwell. They give me fifteen passes before they get too dull to give an efficient shave. 

I've read of some shavers getting over sixty passes from a single blade, but I've never managed to pull that off with a double-edged razor. What's scary to recall, though, is that I used to use a Gillette plastic disposable razor every day for at least two weeks. I paid about fifty cents for each razor, so that means a typical shave ran me less than four cents. Ah, but what about the cost of the shave cream, you ask? I'm a little embarrassed to admit that for most of my adult life, I shaved without the benefit of shaving cream. How was that possible? I got away with this arrangement because my Gillette disposable razors came equipped with a lubrastrip, a bit of foam impregnated with some very slimy gel. It kept irritation at bay as long as I didn't give myself more than one pass; and frankly, I didn't know the difference between a close shave and coconut shell.

The Super Iridiums are my top blade too. Although I wouldn't have hoarded them at the current price (about 30 USD per 100 blades). Personna Med Prep, Black Ninjas, KAI and other St. Petersburger blades are great too.

I would also like to mention explicitly that I have never felt a difference between the new Wizamets and the Polsilvers, both Russian made. They are made in the same factory plant! It is inconceivable that they are differently made.

Anyway, the most important factors for blade longevity you forgot. Since I am using straights, I became somehow more aware of it.

1. Shaving angle/head geometry of the razor
This is the most important factor I think. I compare it to the shaving technique with straights: the steeper the angle, the worse it is for the edge longevity. The same applies to DE or SE blades. I get with Super Iridium or KAI blades more than ten shaves with the tech (flat angle), but only three shaves with the aggressive R41 (steep angle). This is true regardless of the hair type, I hear.

2. Soaking properties of the soap or cream
The better they are, the easier it is for the blade to cut the whiskers, which results in a longer blade life.

3. Shaving technique
The better your technique, the longer the blade lives.

4. Lather hydration
A drier lather seems to be disadvantageous for the edge longevity.

...Anyway, the most important factors for blade longevity you forgot. Since I am using straights, I became somehow more aware of it.

1. Shaving angle/head geometry of the razor
This is the most important factor I think. I compare it to the shaving technique with straights: the steeper the angle, the worse it is for the edge longevity. The same applies to DE or SE blades. I get with Super Iridium or KAI blades more than ten shaves with the tech (flat angle), but only three shaves with the aggressive R41 (steep angle). This is true regardless of the hair type, I hear.

2. Soaking properties of the soap or cream
The better they are, the easier it is for the blade to cut the whiskers, which results in a longer blade life.

3. Shaving technique
The better your technique, the longer the blade lives.

4. Lather hydration
A drier lather seems to be disadvantageous for the edge longevity.

I am not so sure I agree with the part highlighted by me. Yes, the angle is important to the shave quality, but blade life for a DE is more dependent upon the other factors you listed as well as beard toughness. Incredibly, trichologists say Asian males, though often sparsely hirsute, have the toughest facial hair.

...Anyway, the most important factors for blade longevity you forgot. Since I am using straights, I became somehow more aware of it.

1. Shaving angle/head geometry of the razor
This is the most important factor I think. I compare it to the shaving technique with straights: the steeper the angle, the worse it is for the edge longevity. The same applies to DE or SE blades. I get with Super Iridium or KAI blades more than ten shaves with the tech (flat angle), but only three shaves with the aggressive R41 (steep angle). This is true regardless of the hair type, I hear.

2. Soaking properties of the soap or cream
The better they are, the easier it is for the blade to cut the whiskers, which results in a longer blade life.

3. Shaving technique
The better your technique, the longer the blade lives.

4. Lather hydration
A drier lather seems to be disadvantageous for the edge longevity.

I am not so sure I agree with the part highlighted by me. Yes, the angle is important to the shave quality, but blade life for a DE is more dependent upon the other factors you listed as well as beard toughness. Incredibly, trichologists say Asian males, though often sparsely hirsute, have the toughest facial hair.

The steeper the angle of the straight, the shorter the edge retention. And vice versa. This is well known.

The same applies analogously to DE blades. Or how come then the same blade on the same beard (!) has a blatantly different longevity in the Tech (very shallow angle) and the R41 (very steep angle)?

The steeper the angle of the straight, the shorter the edge retention. And vice versa. This is well known.

The same applies analogously to DE blades. Or how come then the same blade on the same beard (!) has a blatantly different longevity in the Tech (very shallow angle) and the R41 (very steep angle)?

Regardless of the angle a blade still has to cut through the same amount of hair. Knives or axes do not dull due to the angle used to cut with. The original hone angle on bare steel determines as well how long the edge will last. Friction causes the wear and erodes the leading edge. In the case of a DE blade the PTFE finally wears away after usage to where the hardened edge then dulls.

Regardless of the angle a blade still has to cut through the same amount of hair. [..]

Obviously.

[...] Knives or axes do not dull due to the angle used to cut with. [...]

I don't think comparing straights to knives or axes is appropriate. And you're empirically wrong. Or how then (!) do you explain the different longevity of the same blade -- for the same thickness and amount of beard -- in a Tech and an R41? I say the only explanation is the different angle.

[...] The original hone angle on bare steel determines as well how long the edge will last. Friction causes the wear and erodes the leading edge. In the case of a DE blade the PTFE finally wears away after usage to where the hardened edge then dulls.

All fine with this and I fully agree. I only add that a steeper angle accelerates the process. Nothing more.

I will leave it at that.

An interesting (to me) occurrence last week that might have a bearing on the topic. In my 55 and older condo community a neighbor comes down from Canada (to Florida) every year. He is 78 and still walks a few miles briskly every morning.

He asked me if I knew of a place that didn't charge an arm and a leg to cut/trim toenails. 

He lacks the flexibility to be able to do this himself.

Long story short ... I cut his toenails for him. I told him to soak his feet. 

He comes down with a bucket of soapy water. While I cut the first foot the other was in the water.

The first foot the nails were tough ! Took awhile to get the job done. I'm not sure how long.

When the other foot came out of the water he dried it off and I began to cut the LONG toenails.

Like butter ! Soaking in the hot soapy water for a length of time made a significant difference.

So preparation, maybe a hot towel before shaving, will probably make a marked difference in blade longevity.

Polsilvers are my favorite blade: sharp, smooth and long-lasting. I currently have one that is on 31 shaves at the moment and it's still sharp, cuts well and smooth. Going to see how far I can push it before it taps out. I have heard of some going beyond 100 uses!