I've done 3 autocrosses and 1 track day. At 12,500 miles my rears were down to the wear bars. The fronts will probably should last me to 15,000 especially with the addition of my camber plates.
2011 E90 M3 ZCP/AW/Ohlins R&T/Vorshlag CP/Stoptech ST-40 Trophy Street
2011 1 Series M Coupe/VO/Fully Loaded/Bloated