I certainly wouldn't want a second hand GPU that'd been used for mining; it'd be ragged.
Some even suspect that crypto mining is better for the card than gaming as it avoids the constant ramp-up/ramp-down of the clock/activity by keeping it pegged at 100%. In turn, that would lower thermal stress.
I think another comparison is with hard drives, which are also used by some cryptocurrency schemes, and do degrade faster with intensive use.
[a]: It's (hopefully) common knowledge in the tech community that purchasing used hard drives is a Bad Idea(TM)
If their data is correct, it should follow that these exact issues will happen on the small transistor process GPUs as well.
Blech, I. A. and Sello, H. (1966). The Failure of Thin Alluminum Current-Carrying Strips on Oxidized Silicon. In Proc. Symposium on PoF in Electronics, 496-505.
The difference in data here is obviously scale, google has -way- more CPUs than GPUs so the absolute counts of failures will be different.
If a given piece of silicon is hosing up a GEMM (matrix multiply), in graphics scenarios this may be invisible to the human eye as it could potentially just introduce artifacts in a scene rendering that could be entirely ephemeral to the frame.
In the case of crypto mining though, it's completely possible (probable?) that there are GPUs that can't possibly ever calculate a proper SHA3 hash (see the paper on AES instructions that fail in symmetric ways).
Power supplies on the other hand... those don't seem to last as long, but we open those up and they are hand soldered by someone in China.
Given their conclusion that this is the result of manufacturing tiny process transistors, it follows that this can occur in GPUs as well.
Using GPUs for mining doesn't destroy them any more than using GPUs to render p0rn videos doesn't destroy them.
I imagine the bearings in the fan might have more wear, however, but that might be more easily fixed.