Damn, that does suck. Especially for BMW, which are known for little bugs that creep up all the time. Kind of sounds like what doctors go through with insurance reimbursement.
On the other end, we used to own a Saab 9-3 Aero. After 900 miles, the rear wheels where covered with brake dust while the fronts where pristine. Took it to the dealer and they got Saab (or GM) to pay for new pads, calipers, rotors AND two wheels. A month later, the rear wheels where black again. We brought it back , and they now said it's normal. Obviously, they did all that original work to make a $$.