Just because you have enough savings to retire doesn't mean you have to retire; it just means you have the option to. And "retire" doesn't mean you have to stop doing interesting work, either. You could keep working an existing job that you enjoy knowing that it's completely optional for you, or you could spend 100% of your time doing work that doesn't necessarily pay (e.g. a startup, or working on random Open Source projects that tickle your fancy).