What's important for the bearings are smooth surfaces, round balls, nice sticky grease, correct adjustment, and smooth operation. The important point is that smooth operation is not enough. A clean dry bearing will operate smoothly, at least for a while. But it will also soon enter the path to permanent self-destruction. When you overhaul you clean, inspect, evaluate, degrease, regrease, renew balls, and carefully adjust bearing cones and locknuts. When you do it again in two years, it should look like no new wear has taken place. If that's the case, chances are your vintage bearings, which may not be replaceable, should go on for decades.
The issues for cables are rust, dirt, strand breakage, free motion, and kinked areas. Free motion is not enough. For the outer cables it's the same except that for good braking the outer cable ends should be finished flat, have a ferrule, and be the correct length. As far as rust and dirt go, it's essentially impossible to clean inside the housing.