Last year was a bad year for me. It culminated in four flats in one day last fall (yes, four! I was on tires that should have been retired). This spring I put Schwalbe Marathon Plus tires on my commuter and I have yet to flat. For me it seems like I start getting flats in bunches when I'm pushing the limit on my tires' lifespan. Then I'll put on new tires and not flat for quite awhile.