Interesting, is the ability to know when to exit a prerequisite? I would think there's a distribution between those you spoke of and some that just picked one thing and went forever.
Well what I mean is there's an ability to see precisely when just enough is done -- no more, no less -- before one can hand things over and exit with sanity and / or dignity. It goes hand in hand. Many work very hard and quit before _the_ critical thing is done, which in a sense forfeits all prior work; others continue working and working and burn out. The best understand something about timing, almost in an intuitive sense. I've seen it again and again, and it's impressive.