The main causes of degradation in electronics are usually material failure due to thermal stress (cycles of expansion and contractor weaken the electrical pathw

The main causes of degradation in electronics are usually material failure due to thermal stress (cycles of expansion and contractor weaken the electrical pathways, resistance goes up, that causes more stress etc.) and electromigration due to over-voltage (the flux of electrons induces a shift in the position of the atoms it goes through). Considering mining is a constant load (not much thermal stress) and improving efficiency requires lowering the voltage those aren't really concerns. There's far less risk than overclocking a GPU for gaming. The only electrical part that may be of concern would be the voltage regulation, but that's still an outlier as long as cooling is adequate. Fans are know to fail because they're ran at high speeds all the time, but they're a commodity.