Campy sells three types of bearings and more are available from the aftermarket. The Athena bearings will be the standard hardened steel, while Record now has a ceramic hybrid and SR bearings are the toughest CULT ceramic. They are all interchangeable.

With mud, it's the seals that are the issue, not the durability of the bearing material. Nothing will last for long once mud gets to the bearings. I'd be slathering the outside with some grease, then carefully wiping off the crud after every ride, not washing it into the bearings.

All of the bearings can be serviced, but it requires removal of the crank to access the inside of the bearing. The Chorus and lower level have a plastic spacer/retainer that can be pried out so the grease can be flushed out and replaced. I used my smallest jewelers screwdriver to pry out the retainer. The balls have to carefully arranged to allow reinstallation of the retainer.