double fan speed = 1/4 the fans life expectancy.
Fans also dont just stop, most of the time anyways.
they get slower and I dont care clean you are, it helps but the fan will slowly lose rpms.
Most people would not notice a change in their card unless they pay attention.
They probably wont notice the fan turning on earlier in the game, or their videocard running 1 or 2 c hotter. Or that their videocard on high has a few hundred less RPMS. (i have 2 of the same videocards, one came used from a miner.. at the same fan percent(about 60%) one runs at 4200 rpm and the other at 3600 rpm. They sound about the same. Really if you get a new card, max out the fan, and see how many rpms it is running. Write this down somewhere, then a few months of mining and high fan speeds(doesnt have to be maxed).. check it again, turn it up to 100% and see what your rpms are.. bet they are lower, no matter how clean your house is.
You can maintain them a bit with silicone lube or some sort of fan lube but they will degrade with constant use.