I have carried a Photon I on my keychain for years (4), and a Photon II for about 3 years. The I is on the original battery, but twice the II got turned on in my pocket, killing the batteries. The little sliding switch stuck both times. Fedex will be delivering my Arc LS on Wednesday <img src="images/graemlins/smile.gif" alt="" />, but it is a little large for the keychain.