That is a hard question to answer. Brake wear is completely dictated by driving style, conditions, type of pad material used, and rotor condition. Cars in cities like San Francisco can burn through brakes in a matter of 10,000 miles or less if driven aggressively, in the city, and on hills where the pads get hot. Heat is the biggest facilitator of brake wear. Rotors what are to thin cause extra heat and premature pad wear. Aggressive driving can cause premature pad wear as can driving in stop and go traffic day after day. When you change your brake pads on a BMW use good quality brake pads and its a good idea to change the rotors to get optimal pad life.