I have used these tires for as many as 10 heat cycles and they still have sufficient grip. They are excellent fro track use in sprint races. For driver school/HPDE/endurance races or very hot days (track surface temp over 100 degrees) the regular R1 compound would be abetter choice, but this is a great tire to go fast on. Data shows me it is just under a second faster than the regular R1 compound on a typical road racing circuit and after the first heat cycle only falls off about .3 seconds.
AS of July 2012, track records in SCCA Super Touring have been set by different drivers on this tire at tracks including: NHMS, Mid-Ohio, Nelson Ledges, Sebring, Homestead, Road Atlanta, Watkins Glen, and Road America, (including a win at the 2011 SCCA National Championship Runoffs.)
The proof is in the results. If you want to win, this is the tire to do it on.