It depends. Most tablet keyboards are powered by replaceable batteries (usually AA or AAA) and can last anywhere from a few weeks to a few months on a single set of batteries. Others have internal rechargeable batteries, which last almost as long, but are a much cheaper alternative in the long run. Keep in mind that if you buy a tablet keyboard with an internal rechargeable battery, it will eventually stop holding a charge, so your tablet keyboard could stop working after several years.