Old MagicBands will work to get you in the parks indefinitely. The issue that you might run into is that if the battery is weak, it might not pick up your ride photos. There are two simple solutions to this. If you have a newer MagicBand but want to wear your old one, keep the new one in your bag. That should pick up your photos. The other solution if you are unsure is to snap a picture with your phone right before getting on the ride. Then give it a day or so. If your ride photos don’t come, you’ll have a timestamp that you can give to Disney when you contact them. They are great at finding ride photos when you have the right information.