Hey everyone, I noticed this with my pre 2 and i've tested it a few times and it seems to work. It seems like the Pre 2 holds its charge much longer if you shut the phone off and then put it on the touchstone or plug it in. The phone will automatically turn on when its plugged in. I do that and let it charge overnight and the next day the battery life is incredible.
Give it a try and let me know if you think it helps.