We normally shoot it off each quarter. The biggest issue we see is rounds repeatedly chambered.
For handguns emphasizing use of lock boxes and keeping guns loaded helps but there is always a certain attrition rate with rifles as they are only kept chambered when use is imminent.
We had a period of time several years ago where our contract with spear for Gold Dot lapsed. We bought a large quantity of Winchester ranger off an FBI DOJ contract however there were quality control issues with the ammo resulting in failures to fire.