I would not think the lights would stay on that long. You can set that via setting menue. I have chronic battery drain issues ion my 07 X5 and it has been at the dealer since Feb 8th.

Things they will tell you is: Did you hit the stop button long enough?
If you tap it is not off but in accessory mode. Blue tooth phone left in car? Had you had any battery drain while parked control messages?
You locked the car and if comfort access the fob was not near it?

All that said from experince I had had my x5 work fine one day and be dead in the gargae the next with no warnings. They may also repalce the battery but I am on my third one now and they may tell you that as it fixes it for now but the new one may discharge shortly.

I would start by maiing sure nothing you can control stays on over 1 minute after you leave the SUV.