"One of the reasons the fronts last longer than the rears is that the front does fewer revolutions per mile. So your results indicates some sort of error. (or you simply never use the rear brake in the city)"
This comment makes no sense to me at all. I wear out rear tires 2:1 because of the throttle...
branthopolis; "LOTS of heavy braking on the front tire accomplishes the same thing to the front tire as heavy acceleration does to the rear, but OP's case does seem to be a very accelerated example... "
As branthopolis points out (for the sake of discussion) If the rear acceleration and the front braking scrubbing were equal ... my point was simply that the 19" front makes fewer revolutions per mile than dose the 17" rear.
While tire brands have slightly different circumferences, for the Avon TrailRiders I use, the math works out like this:
Front 26.1 Circumference 81.9956. 791 rev/mile
Rear 24.8. circumference 77.9115. 840 rev/mile
Over 6000 miles the rear tire does about 294000 more revolutions than the front.
Obviously, digging out of a corner, turn after turn, eats up a tire. I am not saying that isn't true. But the OP is doing his riding in a urban setting.
Always happy to be corrected if my math is wrong.