I don't know if 24 hr climate control even matters. The recent "find" of 400 12 Ga. hand loads had been in an unconditioned storage for all of that time. I know I loaded them, because they had my initials on the boxes and the last time I loaded was 1988. My folks forgot what was in the big boxes of hunting stuff. When I helped to move my dad out of his storage into mine I found them.

As to what goes bad in ammo, the powder / primer could get "wet" from humidity in theory. It seems this would be more likely in shotgun shells since there is no "true crimp" of case to projectile like a rifle/pistol round.