my cleats are still going strong after 3 years, and this is with SIGNIFICANT walking everyday.
besisdes, when i bought SPD clipless pedals for my 3 bikes, they all came with cleats. and when i bought my SPD mountain bike shoes, they came with cleats. i'm still on my first pair of cleats, but i already have 3 pairs of cleats on reserve. the shoes will wear long before i can exhaust my stash of cleats.