. . .I would consider a person equally successful if they are sitting there with ample funds in investments, so that they could continue their current lifestyle indefinitely - and they continue working at their same old job - because they WANT to.

There are a lot of personal definitions of success and I don't argue with any of them. From my experience, I'd say that most people reach a point where they realize there's a finite number of years left - with good health - and things still on their "life's list," and their work or job, no matter how financially/emotionally rewarding, is simply an imposition on living. Some are in a position to make work adjustments and continue on [see Tymmo's "Freedom" post] but most of us have to "pull the pin" to get that independence.

I don't claim to be a typical example, but I enjoyed the hell out of my work for 25+ years [excluding the normal bureaucratic BS] but I eventually got tired of it. I just didn't want to do it anymore. Even if given the chance to continue the work under theoretically ideal conditions, I'd still want to move on to something totally different just 'cuz there's so much more to experience out there.