Well normally i would tell you that revving higher on a stock cam is silly but.........

I decided to look at some N/A d15b dynos and it looks like 8000rpms IS good lol.

For example >

Bisimoto Header
stock jdm D15b head
D16a6 sleeved bore to 78mm.
cometic 80 thousands thick headgasket
stock jdm d15b cam
stock z6 intake manifold
stock ignition
no exhaust
s300
151 whp, 128 ft/lbs tq



In light of this the springs "could" be a decent reliability investment.

To answer the friction question: Yes, in theory. In the real world I doubt you would even see a 2hp loss honestly.