Update:
Took the car in today for minor fixes and asked the SA about this. He sated that the time the radio remains on is based on what the computer feels is the appropriate amount of time for the radio to be on and not affect the ability of the battery to start the car. This is just as Technic stated. I guess I never realized how many tasks BMW batteries do and so an optimum charge is always necessary. I'm use to having the radio on for long periods while detailing the car etc. Time to go shopping for a radio for the garage
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