I could be wrong, but here is what I understand about the Eaton M62 supercharger, as mounted on the M111 2.3L DOHC engine:
1. The unit is maintenance free and sealed for "life."
2. The unit may or may not be rebuildable depending on what tech you talk to.
3. It is a Roots style unit, and the "turbines" mesh together to form the compression chamber. This means that eventually, the turbines will wear and cause loss of compression. But, in certain models (including the M62) they coat the turbines with a low friction compound to reduce this wear. Should add considerable life to the unit.
4. The main wear point will be the bearing set for the main pulley.
5. Pay attention to belt wear. A snapped belt is NOT good. I have a friend with a 1999 C230K and the belt was cracking and worn at 120,000 kilometers, so they seem to last a few years at least.
1998 C230 "Black Betty"