I have heard that story about the fact that I may not be driving long enough from the service rep at the BMW dealership. For one, the BMW engineers are dumb___es if they engineered a car that must be run like that to keep the battery up.
But that is not it. I have had the battery completely drain in two days. I have also jumped the battery to start it, driven 5 minutes, and with that quick charge, it would start again. It is a problem with parts of the car "not sleeping". I would love to send those engineers who designed this to the dunce corner. I expect more from a BMW. This has totally disenfranchised me from the BMW brand. I have owned 5 now and still have 2.