Anyone who's ridden bicycle on California streets knows about all the glass and whatnot, not to mention screws and nails everywhere...
Back in high school, I had a trusty '86 Diamond Back Ascent MTB that I rode 150+ miles weekly, rain or shine, off-road and on. Before the frame broke at the rear dropout in '94, I had put over 40k miles odometer-indicated on it with only 5 flats. 3 of those flats were tire-fraggers from unseen nightime nasties while riding. Tires were at 50psi.
From '95 to '00, I had a '95 Schwinn Cruiser Six, which I rode an odometer-indicated 32k miles before it was (very cleverly) stolen. Only 2 flats on that beautiful bike, one was a tire-fragger. That bike never strayed off-road and tires were 28-30psi.
I'm approaching 2k miles on my motored '05 Schwinn Alloy Seven and haven't seen a flat yet. I just started riding heavily again, now up to 200 miles a week for the last 2 weeks. Like my previous 2 mile-eaters, I only need to add a few psi every 2-3 weeks, keeping it around 30psi.
My method? Nothing but old-school thorn-resistant 26x2.125 tubes, 8-10oz of slime per, and a keen eye for glass and steel banding material (
). Sure, I get a few Predator-blood-looking bleeders here and there, but as long as you keep that tire rolling, the Slime will do it's job for the most part!