I rotate my EDC ammo once a month. Not for reasons of age but because I practice with my EDC and like to shoot the SD ammo.
I did a fair amount of shooting a .45 ACP 1911 in my Naval career. And just as WJH2657 stated, I was always issued ammo that was at least a decade old. I can't recall ever having a problem with any of it.
To the question; IMO properly stored ammo will last many years.