It's not just about outright grip level. When you get faster getting a good feel from your tires becomes more and more important. Street tires and hyper street tires don't always give you the feedback or warning that a race tire provides. When you start finding yourself rolling on the throttle earlier and earlier and trailing the brakes longer and longer that feel becomes exponentially more important. You need to know when you're approaching the limit or you'll end up on your butt. Race tires not only provide outstanding grip, but they are extremely predictable and give you plenty of warning that you are getting closer to their limit by moving around under you a bit without actually loosing traction.
As for a B group rider, sure Q2's are plenty of tire, but I personally recommend moving up to a better tire once you discover you can brake while leaned over and throttle out of the apex to the point where the bike starts complaining because thats when that feel I was talking about becomes very important.
To each their own. My tires are changed every morning with fresh rubber.I dont know how fast u guys are but if your at the track on street tires theres only so fast u can go on them. Stay safe guys.. 
