I know the bearings in my C60 fail due to sitting versus driving. Even with fresh seals and grease, and this time I even made new gaskets for the hub covers, condensation still gets in and I find a rusted out roller every time I crack a hub open.
I don't drive it enough, I know that's the main problem. So I would say, proper grease and install, plus drive it every six months or so at least.
