Hard answer.
You really never know what previous owner used for cooling solution, which voltages etc.
You might get lucky or just an lemon.
I overclocked last year DDR2 ram on 2.4V which is pretty high, they were working for half year and one of them just died. (Yes they are OCZ 800 SLI with heatsink, on review they could go that voltages with fan cooling)
There is always degradation with using voltages, but if they are used correctly with good cooler under specific temperature, it should be fine.