When manipulating your everyday carry, vehicle, or home-defense firearms, you may unknowingly be damaging your ammunition. Avoid creating an over-used cartridge by paying close attention to how you rotate your ammunition.
If you carry or store your defense firearms in condition hot (round in the chamber), you probably carry a full magazine of defensive hollow point ammunition. Because hollow point is expensive (compared to FMJ practice ammo), you are probably ejecting out the hollow point round from the chamber and reinserting it at the top of your magazine, so when you are done practicing with your FMJ ammo, you can easily reload your gun and secure it back into your holster or preferred storage method.
The problem is that every time the slide is sent forward to chamber the round, the cartridge is taking a beating. The tension on the recoil spring causes wear and tear on the baseplate of the cartridge, which protects the primer, a sensitive and necessary component. It is also possible for the bullet component of the cartridge to be compacted further down into the casing.
Chambering the same cartridge over a 3-6 month cycle will probably not result in damage that could lead to a malfunction, and some people manipulate the same cartridge for extended periods of time with no damage. However, it is responsible to avoid possible malfunctions and establish good habits. Therefore, if one hollow point cartridge seems to get loaded every single time, rotate it down to the bottom of your magazine.
SOURCE ARTICLE: https://www.agirlandagun.org/what-is-an-over-used-cartridge/