I recently got into biking, ride about 1,000 miles per season (roughly Mar - Nov, I'm a fair weather rider). My first season, I had 6 flats. In desperation, I bought tire liners, got a flat with those when the edge wore through the innertube. Melted the edges of the liners smooth with a cigarette lighter, have now gone about 1,500 miles without a flat. Just throwing out the tire liner option as an idea. I have Mr. Tuffy on one bike, and Stopflats on the other, they both work well.

I put 6000+ miles on a set of Schwalbe Marathons (moved them to a less used bike) and replaced them with wider and lighter set of Marathon Supremes and have had one flat in 5500 miles with those. I was really suprised when the front tire flatted and it turned out to be a tiny sliver of glass that had worked its way through.

The Supremes weight about 1 pound less per tire and the increased speed of the bike, for me, is a reasonable trade off.

I seem to have a different perspective than many commuters. I don't mind fixing the occasional flat in order to ride lighter, faster-rolling tires. I generally commute on 700x25s and have commuted for years with perhaps 1-2 flats/year riding Conti GP 4000s, GP 4 Seasons, Michelin ProRace, Vittoria Rubinos and the like. During that period, I have tried heavier, more flat-resistant tires such as Conti Gatorskins, Panaracer Paselas -- and I always get frustrated by their slowness and poor ride quality after a few weeks and take them off.

My route has a lot of hills but relatively good pavement, so I pay a real penalty riding heavier, poor rolling tires. However, my touring bike and cross bike are fitted with larger (32mm+) tires and I commute sometimes on them. Both of them have tires that are relatively light for 32s -- Vittoria Randonneur Hypers and Rivendell Jack Brown (greens). Both of those are really nice rolling for wider tires and not much slower than 25s, but worth the extra weight because they ride so much better with fat tires.