buge311
I usually get 2500 to 3500 miles on a set of tire, depending on the quality. I only ride michelin...biaxial sport or bisport axial, I forget, ($22US, 2500 to 3000 miles)) or axial pros ($50US, 3000 to 3500 miles). I seem to get more miles out of the axial pros. my race wheels have pro race. the biaxial sport/axial bisport/bisport axial (whatever) are really great tires for the money. they have tread on them, which I'm not particularly crazy about, but they have a kevlar bead and are $22.
I replace both tires at the same time. I figure if one is shot, the other is close...and a new set makes me feel good. if you see thread/fiber showing, its time for new ones. I'll then use the old ones on my trainer wheel.