You can use any band that is assigned to you, so long as you don't deactivate it in MDX (which you would have to do manually, so if you haven't deactivated it yourself it's still active).
They have batteries for the long-range sensors that are supposed to have a life of two to three years. The RFID chip would still function but not any of the long-range functions (like coordinating your ride photos to your account).