Degradation is definitely possible with overkill voltage, I know its popular to shrug it off but it can happen, although it has only happened to CPU's for me. I have 2 i7-870s die 6-8 months after 24/7 continuous operation with crazy high voltages. Running over voltage will cause electromigration, this is a fact. However as long as you don't go ridiculous (1.3V is really too much TBH IMO) you should be fine since you're upgrading within 2 years anyway. Closehanger, there's really no reason for you to act like a jerk BTW.
So in my opinion a mild overvoltage is fine because you'll replace your card within 2 years anyway. But don't kid yourselves, if you run 1.35V 24/7 for a year you will cause electromigration which will lower the lifespan. It won't be overnight, its not an exact science - it could give up the ghost 6 months from now if you want to run 1.35V-1.4V 24/7. IMHO 1.25V is about the most I would ever run a kepler at , 1.3V is way beyond spec. Its fun for benchmark runs but not feasible for 24/7.