I cleaned my campy hubs on a regular basis and at about 75 to 85 thousand miles I changed out bearing and cones, mostly because I bought some replacements and just wanted to, but the cones were well worn but smooth.

I have a tandem, KHS, no-name hub. Did the great divide, loaded with gear packed in panniers front and back. By the time we were in Mexico I had gone through the original, and two other sets of bearings and cones after smashing both bearings and pitting the cones to the point of being hard to turn.

I am sure the camy stuff was a hole lot better, and for my money it never hurts to buy good stuff, lesson learned. That said the last three sets of wheels I bought are cartridge type and have had zero problems, and if a tandem can't destroy it its got to be good.