Rusty is correct. You will lose heat in a race tire unless you have the pace. It's simple... You are not scrubbing the tire enough to maintain the heat. Think about this - it is 40 degrees out and you are running on a fully heated race tire. You run a 20 minute session at :39-:40 pace. Heat in the tire is lost... Also, if you run out there and the set is fully warmed and you get stuck in traffic, the tires will cool and the feel is changed and you will need a bit of time to get to pace where the heat comes back. If heat wasn't an issue for grip, why have warmers for race compound tires?
You don't run a fast enough pace and the tire will lose heat which can lose grip or become what some describe as slippery or moves under you. Especially in 7 and the keyhole and carousel...
Bottom line is this. A load of crazy info here. Best bet at the pace of :40 plus and wanting longevity on a 600, get a set of Q3s and be done. This whole deal of guys saying they get forever on sets of tires scares the shit out of me. But what do I know? I know I don't cycle my tires that often and feel that the cost of tires are relative to my pace. I will buy good tires to run a faster pace and maintain my ability to push and work on my setup and segment times. You can try and squeeze time out of tires, but honestly is it worth the risk?
For me, the G19 will be my "standard" sized 9mm. I know it's not full-sized, but it's a lot bigger than my PF9, and it will only see carry duty when I have it OWB, not IWB.
The G26 is fatter than I can comfortably fit IWB, and if I were to go that route, I would look at the G43.
...the other major factor is price. I PM'd you.