My Thunderbolt would sometimes last 6 hours and sometimes it would last over a day. I really liked the phone other then that and the poor quality control.
Agree that the thunderbolt battery is a mixed bag. I can tell when the battery is draining fast because of the heat it produces. Obviously, if you are pulling heavy 4g data it will drain fast. But idling I usually don't have much of a problem, but there have been exceptions. Every once in a while the phone will start draining heavy while just idling. If I notice this, I just do a restart and it fixes it. That all being said, the battery life on 4g on the thunderbolt just isn't great. With the extended battery I have no problem though.
Sent from my ADR6400L using Tapatalk