Haha. Flutter noise always caused big arguments over sxoc about turbo wear.
Consensus was though, that it wouldn't reduce the turbo life by a very large percent and would normally not need replacement before the cars rotted. Lol.
If you want more dump valve actuation reduce the spring pressure. If you want more flutter increase it.
What rpm do you normally see full boost at? At 70 you may be at a point that you have very little boost and low throttle position.