I'm sending my Risse Astro-5 back for rebuild and bushings, yet again. I find that the bushings wear out every two years so this is like the fourth time in 8 years. When they wear, I get a nasty clunk through the frame. You think this is a function of the suspension geometry? The Y is flexy and puts lateral stress on the shock. Have any of you had to replace bushing or don't you keep bikes that long?