I remember when I was doing live sound that my mentor would switch out EVERY battery in the microphones EACH show for fresh ones. Those batteries were probably

I remember when I was doing live sound that my mentor would switch out EVERY battery in the microphones EACH show for fresh ones. Those batteries were probably still 75% charged after 2-3 hours, but the risk of accidentally having a battery you lost track of dying during a show was just too high -- easier to replace them all. Ultimately not that expensive in the scheme of things.