I don’t think it really matters how long it was used. Would you buy an 6 month old GPU that was inside a poorly ventilated case where the gamer overvolted and overclocked and gamed for like 4 hours a day? Or would you get it from a miner who undervolted it and had it in an open air rig.
We all know that thermal cycles are what damages a video card the fastest, not the length of use. But gamers are still so misinformed. I think it's hostility toward us miners that makes them willfully ignorant.