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.
1989 E30 M3/Zinnoberrot
2011 1 Series M Coupe/VO/Fully Loaded/Bloated/Stoptech ST-40 Trophy Street