I agree with all that. I've known a couple of people (at least one was out of investment banking--think both were) who pretty much fully retired in their forties, which of course isn't really that young. Some people hit the startup or some other lottery early on and, even if you get a million dropped on you at 25 or 30, you should probably think long and hard about whether you can really just not work any longer. Gives you a lot of breathing room but isn't really a huge pile.

Certainly, there are degrees of frugality. I could probably spend more than I do but don't have a real interest in doing so and generally avoid expensive things that might give me some incremental pleasure but prefer to arrange things so that increment is pretty small and doesn't revolve around "stuff."