It largely depends on how often you have to clip in and out and do you walk in them. For city riding or roads with a lot of stops where you have to unclip frequently and put a foot down the cleats will wear a lot faster than for racers who clip in once at the start and clip out once at the finish line. Also, do you walk a lot in your riding shoes and do you use cleat covers when you do? These factors will determine cleat life, not just time and miles.