I was having this weird problem with my G1. For some reason, the battery charge was not showing a drop. If I restarted it, it showed a change, but when I charged again, it showed either 98 or 99% and just stayed there for days. I had not let it gone long enough to where i never charge it to see if it dies...So, after trying that, I was in a store and about to make a call when the phone went dead.
Turns out, it was a bad device. Had it replaced and has had no problem since..