I've done this twice in the last 10 years and still have a spare in cardboard bubblewrap. They go bad every few years and need to be replaced. They're still fairly cheap, so you may as well buy 2. The fun part comes when you go to pay for them. Take one and put it on the counter and ask the cashier what she calls this (while pointing at the mouse and holding the other one up in the air). She'll say "A mouse". Then put the other one down and in a conspiratorial tone, ask her what she calls THESE. Both times the cashier has said "Mice". hahaha WRONG! That's when you raise your index finger and sweep it across your face, lean in, and using your best voice of wisdom, say "Mouses".