My Cygolite Expilion has started exhibiting a binary fluctuation between normal brightness and dim. Cleaning the contacts (which have visible wear) hasn't helped. What would you do? Risk $40 on a replacement battery or replace the entire light for $90? The light has seen a great deal of use since I bought it 2 years ago and the battery is the original. I have an uneasy feeling that the bright-dim thing may not be related to the battery.