Do whatever you want. Though it seems most millionaires never stop working. The thing is, they're either working simply coz they enjoy the challenge or they want to achieve something more. There are people like that, they grow weak, sick and depressed if they are not working.
Us non-millionaires equate "work" with desk job or manual labor most of the time. They're freakin milionaires, of course they won't do those menial tasks, they'll get someone else to do it for them. "Work" for those who don't need money can be something else like, hunting for new investments, or building a new business, then moving on to something else.