nope. Mine Hold 21PSI all day. Depends on the engine i suppose. Why do you want to change at 8000RPM? there is no reason for that. That's just an engine waiting to go bang sitting on the redline like that. Until you forge the engine don't even go near that. Even then i wouldn't.
Anyway if you are planning on doing hillclimbs get the -7's. You will get much faster times with them. And they can still run decent power. I'm sitting at 320KW on 98. To go -5's for hillclimb is a huge waste of moneys.