Until you power cycle them a couple of times... My old AMD GPU even held a record for how "good" the ASIC still was or was not. TL;DR Yes, your GPU wears and becomes slower over time; eventually it brakes. Not because of bad thermal coefficients but because of the current... Even faster so when OC'ing because U=I*R. You can benchmark it yourself. The broken solder balls of the past where attributed to the transition from leaded to lead free solder. If I recall correctly, it was mostly NVIDIA and Apple who suffered from this and only temporarily / 1 or 2 generations.