That's why I think a Stoptech BBK can save money over the long run. The friction discs cost about the same as an OEM rotor but the discs AND pads last so much longer.
I'd estimate about 50% longer based on the wear rate on my E46. 16 track days, 1 set of PF01s, 31.65mm of 32mm on both front rotors.
2015 F34 328iX GT Glacier Silver
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red