I've read that 1-2 times a year for servicing bearings is pretty common. This amount of upkeep is something I can live with.
I'll pay a shop to do it for me once, watch, and then do it myself from there.
YouTube. I never serviced mine and they were rolling horribly. Once you get them apart, its all visual, and pretty common sense. I cleaned and re-packed my hubs in about an hour and a half. I'm sure that the next time I do it I can cut that time almost in half.