All shocks settle in. You probably either haven't noticed it or the sidewall on the 15s eats up all the little bumps. In my opinion extra rebound is good for a stronger spring. Koni's come with a lifetime warranty so if they do wear out a little earlier its not a biggie.

Quote Originally Posted by BigKriss
"Koni's are supplied with the adjuster at full soft, as this is the recommended setting for the particular vehicle that is to be fitted with Koni's. The adjuster is primarily a wear compensation device, and should be used only when necessary. Do not overadjust." Source

Intersting I have H&R springs also. I only run at full soft and can't work out why other members on here wouldn't do so otherwise. After 12,000 miles, I haven't felt any softening up yet and I would assume that there is something wrong with your shocks if they begin to soften up after 3,000 miles.