I've had bands where the battery only lasted about 2 years... There is no way to test the battery. The only way to know is to go on a ride that auto links pictures (like Pirates or Seven Dwarfs) and see what happens.
So when using older graphic bands (like my MK45 Tiki, or Pandora opening) that make special effects at the tap styles, I also keep an icon/puck from a new solid color band (which is also linked to me in MDE) in a magic keeper attached to my bag or belt loop. (I replace the lanyard clip with a 2" carabiner) That way I get the best of both... effects when tapping the older special band, and long range stuff.