Sealed bearings on bike parts are usually good for a long go. Nowhere near like you have to replace the cartridge every time you would re-grease regular bearings. For instance Rivendell says you don't do any maintenance on the PW bottom bracket until arouns 15-30 thousand miles.
If you can lace them yourself you can get the phil 7 speed freewheel hubs for 105, and 95 for the front. then you add rims for 20-50, and spokes, you have a pretty unbreakable combo. You can't get the cartridge hub for the cost of a pair of freewheel wheels. & is more than enough when you actually look at what most people are touring on, 11-34 hubs for instance, where the next spoket is a 12, just not usefull on a touring bike. Phils have hardened axles, as do Hugli, not sure anyone else does.