They don't wear very fast unless you really push it. There is also a groove or slot wear indicator cut into the pad. When you can no longer see that slot it's time for new ones.my wing has 11,000 miles on it and when i took the front tire off to mount a new one i noticed the pads seem thin ( i'm a subaru technician) i measured them and they measure 4 mm thick im used to automotve pads which are 12mm new so just concerned. but it sounds like there around 4mm when new? thanks