Being that you can adjust the delrin spheres, and with the chrome plated ball, I doubt you'll have to replace them very often, and the delrin cups are only $4 a pair if you do actually end up wearing some out.

Do you think I could find a place that would be able to chuck that housing they come with up in a lathe and turn them down to 5/8" thread for the spl rear arms ? I checked with them and they said they dont have plans to offer a 5/8" any time soon