There was one spot on my commute that kept giving me trouble, even with liners protecting my tubes, so I upgraded to specialized armadillos and haven't had a flat in a little over 2,000 miles. before upgrading tires, I averaged about one flat every two weeks. That was just down right awful, there isn't much worse than being part way through a commute and having to pull over and change a tire in the freezing rain. It is really difficult to use a tire lever when you can't feel your fingers, and your sitting in a pile of snow. While I still carry my tool kit with patches and a spare tube, I refuse to accept 2 flats per month as normal wear and tear.