ExtremeTech - Buyer Beware: Crypto Mining GPUs Lose 10 Percent Performance Every Year
 
“According to Palit, a GPU will lose about 10 percent of its total processing power for every year it’s used in a mining operation. Even if you get lucky and your second-hand GPU works, it might not be running at peak performance, and it could be closer to failing. Still, this might be a tempting option for people who are in desperate need of a GPU, as the prices for new cards are still much more expensive than they should be.
 
It is, of course, in Palit’s interest to have people buying new hardware, but it’s not like Palit or any other manufacturer is having trouble unloading GPUs. The company notes that if you are going to buy a former mining card, you should take a look at the cooler. Any card that has been disassembled and equipped with an aftermarket cooler is a big risk.”
 
I actually would have thought that the degradation would have been higher.

But its the best way to supplement such an expensive component for your pc.

Assuming your minnig 24/7... maxed out over 100 degrees? Even then after 5 years you made many times ROI and ready for a new card anyway...

I think it depends on where they obtained the card(s) for testing.  If it came from a home or small operation where the equipment is cared for properly in a controlled environment, then it might be fine.
 
If it came from an operation in a dirty/dusty uncontrolled environment with no preventive maintenance, then the cards performance will probably be degraded.
 
 

I think a lot depends on the conditions, i.e. political, legal, etc., where they are operating.

I am already seeing people dumping those old 5700xt trying to get some $ back. I guess those miners need the fund to buy next batch of GPUs to mine.