This is a good time to rehash some advice about storing ammo.
1) Moisture is the enemy, whether it's in the form of humidity or leaking water. The storage environment should be protected from both.
2) Extreme hot and cold is IMHO not as bad as rapid temperature swings because changing temperature causes condensation.
3) Ammo should be kept in a reasonably watertight and airtight container, but not a particularly strong one- you don't want it to turn into a bomb in the event of a fire.
4) I recommend against cardboard containers unless they're kept in a watertight environment. Cardboard will wick up water and hold it like a sponge.
The storage area may be indoors, but remember that roofs can leak.
All that said, ammo should last for decades inside an average modern American climate-controlled and leak-free home.
However, as other posters have also said, I dispose of my carry ammo and replace it at least once every ~3 months.