I know that ammunition properly stored will last almost indefinitely. That being said, ammunition carried every day is not in storage under ideal conditions and is subject to weather, humidity, sweat, etc. Because of this about every six months or so, I cycle the ammo in my carry sidearm and spare magazine through at the range and reload them with fresh. Doing this incurs some cost but it is a small price to pay to make sure that if I need it, my gun is going to go bang.
I’m interested in other peoples thoughts on this subject.