For you guys who use Snark type clip-on tuners - how long do you get out of a battery? I have a couple of them, and don't use them all that much (maybe at the beginning of rehearsal/gig, and once or twice in the middle), but I feel like one of them always has a dead battery. I am pretty careful about turning them back off when I am done. Other electronic gizmos seem to last years before the battery goes, but with Snarks it seems to be a few months.