[#nerdalert]
So, at the expense of potentially causing further pain to @MDU, even if the battery fails, I would expect the vast majority of the magicband functionality to remain.
The passive portion (not powered by the battery) is anything where you have to hold up your band to something else for it to work. So, any mickeyglobe functionality (entrance, payment) and room access are most likely using the passive RFID which should work in perpetuity (until electronics failure). The active portion that uses the battery is sending out a signal in a ~15 ft bubble around you. My guess is that this is what is used for the interactive Mickey at town hall. There is a more limited amount of info that is being broadcast this way. Disney doesn’t want your band broadcasting a payment in a 15 ft bubble because everyone in line to pay would be registering payment for whomever is checking out. (similarly, you don’t want to pick up everyone in line for entrance, just the exact person at the globe).
So, magicbands should work for the passive stuff for a very very long time. Second, just because the magic band works for entrance and/or payment, doesn’t mean your battery isn’t dead and that your band is fully functioning.
[/#nerdalert]