I added Redline 5W30 @ 1200 miles and again @ 5500 miles. I am now @ 10,500 miles and I am going to be changing my oil again any day now. Redline 5W30 of course. Aircraft quality synthetic with a flash point up over 400 degrees F. I won't be using BMW's "free oil change" but the rest of their free maintenance I will. Like new wiper blades every time I go in for service/repairs.
Waiting 12-15k miles is too long, but I don't know if you can change that. They allow you to change your own oil as often as you want. The car will last well over 100k miles even if you only let BMW change the oil every 15k. I think for anyone to care (like a court) engines would have to fail, due to the extended oil change intervals, well before 100k miles.