I've used a Shimano Alfine 8-speed rear hub over the last 3 years. It has performed flawlessly. Zero maintenance there. Front hub is old Campy Record. Headset and bottom bracket are Suntour Grease Guard. 5 minutes to inject new grease every 6 months or after every very wet ride. 2 new chains and one new chainring every year. 2 sets of brake pads per year. New rims (not wheels - rims) every 1-2 years.

For a derailleur-based system, with traditional components, maintenance would be higher. For me the tally would be:

• 4 chain replacements per year (derailleur compatible chains wear faster)
• New cassette and chainrings every year
• Overhaul both hubs twice per year. BTW: Shimano hubs are generally better sealed than cartridge-bearing based hubs, and are easier to service. If you ride in the wet, there is no escaping the requirement to overhaul hubs.
• Replace bottom bracket every 2-3 years
• Overhaul headset every year.

Riding in the rain more than anything, kills bikes. Wet and gritty conditions are worse.