I used to do periodic (annual) maintenance where you strip the bike down all the way, but these days I'm down on that method.
Reason - I've pulled apart my bike several times and found hubs that were perfectly fine, needed no overhaul. Also, you can get water invasion into a hub and it will "go bad" very prematurely. There's no predictibility as to when it needs work.
So now I like to do frequent, close, functional inspections, like every 15 - 30 days. I catch more problems before they get big, and don't waste so much time fixing things that aren't broken.