The RT-615s used to be the tire to have in STS, but not anymore. They're not a bad tire, but you won't see more than about 10,000 miles out of them.

I DD, track, and autocross the Toyo Proxes 4s. The first set lasted 30,000 miles, roughly, with I think three or four track weekends and maybe 10 autocrosses...or about 50+ autocross runs on them. The track weekends were driven mostly by my roommate at the time...he time trialed my car for three events, and is a much, much better driver than I was at the time. Well, by better, I mean Rob hustled my car around a road course faster.

I replaced the Proxes 4s with another set. I've now done two autocrosses, and five track days on them. I've had a couple of my instructors comment on how well they stick.