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.
The only issue with mining rigs are the fans. They generally wear out much quicker than some gamer. Since gamers generally only play 1-2 hours a day, usually the fan doesn’t spin at all during that time. Compared to a miner rig which had it running 60-70% fan speed for years.
I don't know what games you play but most pc games are pretty gpu intensive these days and those fans spin as fast as the gamer allows them to spin.
No different than miners adjusting their fan speeds.. in otherwords, the games today can make a gpu fan spin at 100% if the gamer doesn't intervene.