With that modest voltage increase you won't have voltage related damage but rather temperature related damage. I can't agree that GPUs are able to withstand higher temperatures, nor that they last longer running at any particular temperature... rather they are more conservatively clocked so they stay stable at higher temperatures... till you o'c the heck out of them.
Generally speaking for long life you want a video card to stay under 70C, but everyone's definition of long life will vary particularly for gaming use. I do suspect it will last longer than two years if kept under 90C, unless the fan craps out early.
On the contrary a more serious problem with GPUs than CPUs is broken solder balls since they are directly soldered to the PCB instead of in a socket. That didn't used to be as much of a problem but these days the huge power state changes cause so much expansion and contraction of materials that do not have the same coefficient of expansion.