Ever had products go rancid?

Not rancid, but i did have a tub of soap turn into goo.
Think "Elmer's School Glue" . . . .

All of the artisanal soaps that I have had have been just fine. The only thing I have noticed with many of my five to six-year-old pucks of Mystic Water is that they have hardened quite a bit, but they still smell very nice.

Yup! Won't share the artisans name because I don't see how that will do any good but I took the lid off a tub and smelled rancid oil. Assuming the super fat fraction in the soap went off. Hey, I have too many soaps and it's my own fault not using them up fast enough. Enjoyed it while it lasted and it was getting close to done when it got lost in the back for a few months. Shaved great but the rancid smell was more than I was willing to endure just to kill a soap.

About the Simpsons Aftershave Balm, I am on my second tube and while the second one has not gone bad, I much preferred the consistency of the first tube... initially. I didn't start the second tube until I finished the first so I don't know if time was the culprit or there was a complete inconsistency from one tube to the next. I'm guessing time because the first tube began to get runny towards the end. Also, since I don't use Simpsons Aftershave after every shave because I have others that I like, as well, it takes me some time to get through a tube.

Oils can definitely go rancid and the Simpsons product is largely oil.

I've had croap, lose scent rapidly, yes Cella was the culprit, and others change character as they age. But I've also used soap from the '80s and it's absolutely OK. Understand that I have no idea what the scent was like when it was new.

Savonerrie du la Moulin of assmilk fame comes in a ashwood 'container' not unlike those European cheese rounds. There is a loufa pad theoretically to help drain liquid and dry the soap out between uses. Mine turned into a soggy mess of discoloured soap underneath the dried puck that had all the charm of sourmilk.

Ah yes, sour milk is charming.

Fortunately only one so far, but that was a CRSW Vetiver.

I have never had anything other than a food item go rancid. If soaps or creams are stored for years and years, then yeah, I can see how they might go a little off. Consumables are meant to be used fairly soon after they are bought, and might not have an infinite shelf life. Even so, I have seen soaps and creams that are several years old that were still usable. The soaps might dry out a bit and harden, but they were still did the job.