Well, lets see. . .
There were about 20 in our class last week. The instructor pictured below gave rides to about 75% of the class, except for the last two. The last two didn't get a ride because the left rear tread seperated pretty seriously from the rest of the tire.
But to qualify the "ride," there was some major two-foot driving, sliping the brakes and standing on the gas, going on. The result were these hellacious 2-300 foot smokey burn-outs, as well as some major sideways slipping around every corner of the autocross course.
So I'll say 13 -- you can get 13 smokey-burnout-rear-end-hanging-out-at-every-corner trips out of a set of (very well used) Pilot Sports.