I'm with Richard. The 9mm Parabellum is a high pressure round (38,500 psi) so that little recoil spring is what keeps the slide from battering the frame to death during recoil.
There have been pictures posted of wear on the frame down below the rails. I think most of that wear occurs when the recoil spring has gotten weak.
Hey, look at it this way: At about $5 per spring, that's like 3 or 4 rounds of premium ammo at today's outrageous prices!
So we should all do ourselves and our R9 pistols a favor and replace those recoil springs sooner rather than later.
Steve