Like Pmackie I also wear out the sides of my front, but the center of the rear. The BT-021s haven't shown any sign of wear until I did a 9 hour trip up to and around the allegheny national forest in NW PA. It flattened a bit since we were too tired to ride twisties at the end of the day.
Previous tires include:
Stock Battlax - 5800 miles, 4600 from previous owner. Rear center was bald.
Pirelli Diablos - immediate grin upon replacing stock battlaxs. Got 3000 miles before the front sides were paper thin and the rear tread was smoothed out.
Pirelli Diablo Stradas - no increase in mileage, probably due to under pressure and a nail puncture. Fronts still wear too quickly on the sides and I might have killed the rear wear with low pressure due to the nail. ~3000 miles Slightly better wet feel than diablos, especially with the front.
4th set is the BT-021s - Have about 2000 miles now, front sides are down but I can still see tread. Rear is in good shape, with center wear evident. Wet grip is outstanding, and may build overconfidence. I haven't slipped either tire in the wet. Dry grip is great. Very happy with these tires, but hoped to get >3000 miles. I might get that from the rear but the front is on pace to get replaced at about 3000 miles.
Luckily I change and balance tires myself, so each replacement is about $220 total.
Anyone with suspension, pressure, or other suggestions to improve mileage would be appreciated.