I've recently got into mining and therefore put my GPU (7870) under a fair amount of usage. I mine at fairly low intensities (12 on cgminer) and occasional higher intensities for a maximum of 8 hours at a time. During this time the temperatures hit a maximum of 64 Celsius. I know this isn't a temperature to panic about but I was wandering how this would affect the longevity of the GPU.
Also I was wandering what takes it's toll on the GPU's lifetime, usage or temperature (I'm not talking extreme temperatures, more like ~60).