I'm in my 40s, so I've started thinking about it. You know what? I can't see myself retiring, and it's not about money.
I just wouldn't know what to do with myself other than become a couch potato. I've already travelled the world as much as I care to (and have a bit more travelling to do to keep the spouse happy).
I'm not rich enough to just do 'whatever', but have more than I need to get by. Unless I win the lottery so I can fiddle around on a large scale, I'll keep working just for something useful to do.
What retirement looks like for me is slowing down, not stopping.