FWIW, i've been flying these since 97 and never had a Rocket City ball link fail me, either by popping off or breaking. Can't say the same for other brand links. I never had problems with Hirobo linkages, but it was a personal thing to change out all the z-bends and use RC links in their place. I did this even when I was a rep for Hirobo/Altech, and I had no problem telling other owners to do the same.

This is also part of a maintenance issue. Nothing on a heli has a permanent lifespan, and everything has a service life. If you feel a link providing too much slop, change it out (balls are suspect too). If a bearing feels rough, change it out. If fuel tubing is too soft, change it out. Replace your batteries once a year. This is just the tip of the iceberg!