To be honest, I am a little baffled as to why people are breaking the. I'm still on my original BD7 13' DCJ's which came with the upgrade pack (2 years ago?). I can't remember who it was, but they mentioned specifically to rebuild them once you open them up from the package. Cleaning, and re-greasing them were integral to extending their lifespan. I took his word for it and (knock on wood) I haven't had any problems since.
I run 13.5 boosted on carpet.