How long can I leave handgun ammo in my personal protection weapon and still expect it to fire?

How long do I have before I change out the ammo in my carry gun. I always change around the mag ammo and the one in the snout because I know the lubricants have been know to cause a round to not fire, and i also switch out the ammo in my gun and the extra rounds in the box every two weeks, but then again it goes back in the gun 2 weeks later. I fire remmington gold sabre 9mm 124 grain and whinchester white box personal protection 180 grain 40 S&W, all hollowpoints