I'm glad that they took care of you. I knew they would, I just didn't know if it could be fixed locally. What a bummer that you got a truly bad one. What a lousy experience to go through as a first experience.
Yup, same thoughts here about full brightness. Don't stare at it, but if you turn it on and back away, try looking into it. It can be used as a temporary weapon is my point. Generally I use it at full maximum efficiency and not max' output ( one blink of the switch light. In ramping I go to 2 blinks of the switch light then back it down to get one blink.). That does most outdoor things for me and the cells last an incredibly long time used that way. 2 blinks of the switch lights means it's moving into a more inefficient mode. I don't know of any BLF light that doesn't allow the LED to be overdriven. That's how they achieve the output. Using it at saner outputs also lengthens the life of the LED and not just cell charge. If the life at max' output might be 25k hours, throttling it back might result in 100k hours of life. Of course the light can still enter turbo mode with a double click. Yeah, it's nice to have that when needed.
I also have been using it as a nightlight (tail standing it) with a dome. On minimum output one doesn't even notice the drain on the cells. That was using 30Qs (3000mah), now I've gone to 3500mah "GA" cells and I'll notice the drain even less, but in theory the max' output won't be as much. Something that I rarely ever use anyway. I'll never notice the difference in output by eye. Using it with a dome also turns it into a credible "lantern" for a power outage. Staying within "one blink" makes a room not flooded with light but easily navigable. Using the 30Qs I could use the light for a nightlight every night and use it for outside illumination (rural Maine is truly dark other than what we make for light, or what's supplied by the moon), and after 2 weeks I'd still be at 4 volts as told to me by the light (3 clicks gives a voltage readout in blinks). I think with the GAs I'll check the cells once a month and even at that I bet I don't drop below 3.8 volts, still above 1/2 charge.
Of course ceiling bounce (tail standing) works for room illumination, but I've been using these domes and while not a precise fit they work fine and are heat resistant.
https://www.batteryjunction.com/fenix-aod-l.html
A dome is more efficient for lighting a room than using ceiling bounce. The Q8 with a dome can make one a sort of Gandalf ("You shall not pass!" If you saw the movie.) , especially at full output which is pretty serious light output.
Anyway, I'm glad that you finally got a working Q8. It won't make you feel better but your light was a true rarity and maybe the only totally non functioning light of a thousand or so..
Brian. Lover of SE razors.