Depending on how much I ride my clipless, I go through 2-3 sets of Time ATAC cleats per year, but they also get walked on a lot. I'm pretty conservative about letting them wear too much as I always replace them before performance starts being degraded. I'd rather drop a few bucks now and then and just be more secure than wear them longer and start pulling out unintentionally. That said, though, the ATACs are great in that regard.

Incidentally, anyone know where to get the best deal on ATAC cleats?