As a frequent offsite trip taker with my family (GASP! I know! The horror. But listen: I have 2 grown kids. We can either stay for 10 days offsite in a nice big rental house where everybody has their own room OR stay like 73 hours in a suite onsite) we are quite familiar with using MagicBands on offsite trips.
The reality is nothing explodes. Not the band. Not your wrist. Not your wallet.
MagicBands DO work for subsequent trips. I have a giant stack of them that I take with me every time I go because I am the kind of girl that likes to color coordinate her MagicBands to her outfits.
(I'm kidding. I can't even wear shirts that coordinate with my pants. I bring a stack of them because I tend to LOSE them.)
BUT - they DO work - even if you are offsite.
The difference is that if you aren't staying onsite your band is limited in its powers: It only works as an alternate to a ticket (meaning you can use it to get into the parks AND to redeem FastPasses).
You can't "charge to your room" (because you aren't in an onsite room) and you can't redeem Dining Plan credits (because offsite people don't get the Dining Plan) BUT they can still come in really handy for getting into the park and for your FastPasses.
We have a post all about the benefits of staying onsite BUT for each benefit we tried to highlight offsite alternatives. Clearly not everything can be duplicated offsite (like the Dining Plan) but this might help you if you are pondering the pros and cons.