I was at MK yesterday on a 4-day FL resident ticket. I used to have an AP but not right now. I saw the MagicBands for sale and asked a CM if I would be able to use the band on future visits. She said yes, but the battery is expected to last for about 2 years and then I would have to buy a new one.
This surprised me — I guess I didn't realize they have a battery. But what if I come back in about two years, with my new ticket loaded onto my old MagicBand and the thing doesn't work at the entrance? I imagined loads of people in two years may have this problem, creating delays at the turnstiles. Or what if the battery dies while you're in the park and you left your wallet in the car? That would be unfortunate.