Firstly its worthwhile considering whether the need for any bearing service is thought to be necessary at all. Much depends on the knowing what use any bearing has had whether it be our own or on a purchase made from from some unknown scource . A regulary serviced well oiled hub will usually last a lifetime on any looked after machine. With the new water proof repellent greases available makes this task less needed , having said that I've just recently dismantled some Chater Lea hubs from 1952 filled with old post WW2 (cart) grease hard as a bullet and the cones, cup and ballbearings were perfect.
I suspect we have all experienced Garth's problem but I would suggest one should use new good grade ball bearings as their cost being miminal along with a good class grease it can certainly improve the running of the finished job. Any restoration of bikes tends to have slight imperfections after we have tried hard to preserve and give our best in bringing something back to be like new again.
Its "Swings and Roundabouts" I believe as the saying goes!.
Doug Smith
North Dorset
UK