I have automated 80% of my site maintenance. Beyond that I have volunteer mods and super users helping take care of much of the daily on-site tasks. I could technically disappear for years and the site would go on without me. All revenue is direct deposit into accounts that are linked to accouts my wife can access.
The main hole would be having someone to reply to emails. But I am working on automating that as well.
Then I shall disappear. [insert sinister laugh]