[carguychris]

Ammo can go bad if it is stored in a wet environment, or someplace subject to wide temperature swings that can cause condensation.

OTOH ammo that has been stored in a reasonably cool and dry environment can last for many decades, even for over a century. Most climate-controlled homes are perfectly fine for long-term storage.

If the rounds look nice and shiny and there's no sign that they've gotten wet, they should be fine.