I don't know who you are yet but it's a very cool post and now I'm following =D. A great man Howard Bloom once talked about how he never plans on retiring. An old man himself now, 75 I think? And he is still active. If you manage to do what you're passionate about, why not do it until your dying breath?

I'd rather aim for that than the old-hat idea of planning ahead so you can sit comfortably in a chair for 20 years...!