Hello and welcome to Just Answer.
This is just the way the tires wear. I would say average life is 18,ooo to 22,000 miles. There is nothing that can be done to decelerate the tire wear because of the suspension setup. The cars suspension is set up this way for good handeling, not good tire wear. This is just part of owning a performance-suited vehicle.
BMW Master technician
BMW S.T.E.P. graduate, 10 years BMW dealership experience