I've never had the battery go dead so far. My TCH is 19 months old. I have only used the defroster a few times.

I almost killed the battery once by turning the parking lights on, instead of turning the lights off. I know, automatic will do it for me, but I often just turn them off when I park. The lights were on over night. I was amazed the battery still had enough power to power on the computers in the morning.