A cabled mic is always a good idea for any mission critical wireless mics. In my wireless mic box, Shure one that came with a wireless system, I have a hand held, a body pack, a headset for the body pack and a guitar cord for the body pack and 5 pairs of NiMH AA batteries. I rotate the batteries so I'm always using the oldest charged ones, but I use at least one pair every week and usually use two. At the end of rehearsal or a gig, I leave the mic/bodypack on so it will run the batteries down. Then I place the discharged batteries in my charger the next day and move all the batteries around for the next use. Been doing it this way for quite a while, and so far the batteries in my mic case rarely fail. (And the charger catches any that will no longer charge.) I'm consistently getting at least 5 hours use on charged NiMH batteries. (I hate throwing batteries away and this way I don't have to as much. The fact that it's the cheapest way of using batteries doesn't hurt either.)