I watch where I ride and use a quality inner tube and kevlar belted tire. So far so good. On my old commuter 3 speed that I rode from 1982-1987 I could change the rear tube in less than 5 minutes. Once you learn the technique it isn't all that hard. Hell it takes a good 15 minutes+ to change a car tire and you have to do that where you stopped, with the bike you can push it to a shady or dry spot depending on the weather. Even on my 8 speed city bike a rear tube change is only 15 minutes and that one has a chain case.

Aaron