Time attack is great, like a giant autocross but you get to stay out for 15-20 minutes, get the car up to temps, brakes, tires, get clear of traffic then go all out for a lap or two then cool off a bit, think about what you want to do differently, hit it again...., do a few of those sessions in one day and autocross becomes a bit less interesting, albeit far less costly. I will autocross but only when I cannot get on track and hopefully longer courses and fun runs!