You can probably be a bit more generous with the voltage - people have been getting cautious lately. 1.45 is well within the safe region, and if you have to go to 1.5 you _should_ be okay (as in, you'll reduce the lifespan, but it likely won't be noticeable)
Naturally the higher the voltage, the more risk of frying the chip outright - but 1.5 should still be safe for a fair few years