what the hell are you walking through that would cause that much wear, a shredder? I used SPD-SL's for a few years and outside of a little wear on the front pads, they looked practically brand new after 5-6K miles. If you are seeing that much wear, I would wear a pair of slip on shoes to where you park your bike, they will run maybe $10 and last a long time, or move to a MTB pedal system like Time ATACs or SPD types.