I don't have a BMW, but I'll toss this one out: When you had your system set at 80, did you have an open window or something, i.e., did your heater have to work really, really hard to keep the car at 80? My brother drives with the heat on and an open window routinely. He likes the contrast. More to the point, he likes the cold breeze in his face, and his wife doesn't want to be cold. This is the same one who woke up once with two inches of snow in his room. (Ok, just near the window, but still!)

-jk