well a spring would theorhetically never need to be rebuilt (or at least less often than a hydro). but this could be argued. people don't seem to give it a lot of thought as if ones better than the other unless they're using a highlift cam. the extra lift is what wears out the old style (hydro) or prolonged use (high mileage). honda released the spring type later with a larger contact patch to increase protection to the cam. you can buy an even stronger spring type or you can go with the later model spring types from the itr/gsr and or h22.