Do you ride very close to the curb where there may be more debris or broken glass? Outside of pinch flats on the MTB, I haven't gotten a flat riding....ever? Seriously - since I took up riding again a few years ago, the only flats I've gotten have been on the MTB when I do stupid things that cause snakebite. Never gotten one on the fixie. I've run a variety of tires, mostly Conti Ultra 2000s, currently a Hutchinson Carbon Comp and a Specialized All Conditions, a Conti Ultra 3000, and even an old 27" Trek tire. Never flatted on any of them. I tend not to ride in the gutter and run everything at 120 psi, but past that I can't come up with any reason for my lack of flats outside of luck, and luck doesn't really cut it as an excuse one way or another. I'm rambling now. Time to end post...