Data point: I bought six Nitto NT-01 tires at the beginning of the year for the historics 914. I've driven three weekends thus far:

- Thompson Historics. One 20-min qualifier and three 20-min races;
- New Jersey Historics. Two 20-min qualifiers, three 20-min races, one 40(?)-min 'bonus' HRG race.
- Lime Rock Historics. One ~1 hour jaunt on backroads to Falls Village green and back to LRP, one 45-minute qualifier, two 20-minute races.

(Session counts are from memory; may be more or less).

The initial four tires are still on the car. They are driving the same as the first time I drove them at Thompson. Plan on driving them at Thompson again in October, not even going to rotate them.

I've rotated them once (cross), before the LRP event, just "because". The other two new tires are still on the tire rack in the trailer, haven't touched the ground except to get rolled into the trailer. I can't tell if they're worn. I've attempted to measure tread "depth" of the old ones compared to the new ones but it's hard to say, since the "depth" on new is actually higher on the old ones due to light debris pickup to/from pit lane/trailer/garage (I was on asphalt all weekend at LRP).

These are 100TW tires.

$860 delivered from Discount Tire for all six (coupon and a rebate card). 205/50-15.

Just a single anecdotal data point.