Well just from what I've read only expect to get 10-15K out of a set. I have a feeling most people that buy these tires drive their cars hard. You should probably check out
SCCA Forums for more information on the tires. Check out the STS / STX section. I'm sure you'll find a lot more information there.
I think a limited selection of sizes is the big problem. I believe they only make these in 6 sizes or so, most of which are 205's if not all of them.