Being a daily rider in a very wet and grimy environment I do chain maintenance on a weekly basis.

1. I wet it with a solvent lube like White lightning dry, or Finishline dry.
2. I spin it for a minute or so then wipe it, and jockey wheels with paper towels, and then a terrycloth rag.
3. I repeat 1 & 2 when really dirty.
4. I put a drop of Chain-L or White lightning wet on each link then spin the chain for a minute.
5. I wipe with paper towels and terrycloth rag until clean and dry on the surface.

I don't keep track of mileage but they seem to last at least a year+ so I would guess 6k to 7k miles.

On my bikes with chaincases, I oil them once a year and they last for many years.