Moisture/humidity is more of a concern than temperature. As stated, rotate your ammo so the same round isn't being chambered. Shoot your carry ammo and replace every so often (most police depts. mandate this ever 12 or 6 mo).
Only you truly know the conditions your ammo is in. If you are finding a lot of crud around the primer, bullet discoloration, changes in the seating of the bullet, a lot of scratches on the rim from several extractions.......change it out.