The life of my card and a few misc questions

I'm currently using a 6800GS and I'm toying with the idea of a vmod. Does the lifespan directly corralate to temperature, or are there other factors involved? I've also heard people say the lifespan of your card will be shortened, do they mean instead of lasting 5 years your card will last 4, or instead of lasting 1 1/2 years your card will last 6 months? Right now my temps are about 61 peak load (I.E. ATITool for 30 minutes) at 500/1200 and it gets to about 56-58 when I play games. Is it safer to go higher?

Sorry for all the questions just stuff i've been wondering. Thanks in advance.

I think typically MTBF is ~10 years. for everything but fans.
And overvolting will probally knock 2 years off that at most. Even if temperature is controled voltage still removes live becuase of increased electron migration.

well $417 what have i been waiting for thanks for the answers