Hy britcon, brake lights on for an hour will bring the battery down, but I wouldn't think it would deaden it. That certainly would not account for the battery going dead while you drive, a bad battery, HEAVY draw, or charge not reaching the battery could cause your problem. You have already replaced the battery, and the alternator, so common sense would say you have a HIGH draw somewhere, or the "charge" is not reaching the battery. Hope that helps.
