Usually our sound designer gives a speech on the responsibility of having a mic, and that they are expensive. It is usually more about offstage talking and missed mic cues, than breaking them though. We would use the "if you break it you wont get another" tactic, but the whole deparment knows we have forty, and for any given show we only use thirty, so that wouldn't work. Regardless, the asst sound designers mic the actors/actresses in their dressing rooms before they are in costume, then the costume is put on, the makeup is applied, and then we do a mic check. Right after the show, while the performers are getting undressed, once all the essential costume pieces are off, the mic is immediately removed. As a sidenote, we keep our mics in four seperate rollong rackmount carts with locks that require two keys, so that a) it takes the Student TD and the Student Sound Designer to open any of them, and b) in the case that something should happen to one of the racks, we would have only lost ten mics, not all forty.