I think that if you have the drive to get to that point, you have a mindset that's not going to be satisfied with quitting.
It's like the folks who work extremely hard at amateur sports. They're not going to be content with placing in the top 100. "Welp, I made the top 100. What a ride. Alright, I'm good. I'll keep cycling, but I'm not going to be training as hard anymore." They're looking at what they need to do to get into the top 50.
Why does Paul Graham do what he does? He didn't even need to start Y Combinator. After Y Combinator had a bunch of success, he could have retired then, too. He's still plugging away. I assume he gets fulfillment from winning in a competitive marketplace, because he could, at any point, say, "Wait, why am I bothering with this? I'm rich!"
The fact that he's still working is an indicator that for some people, work and business is just as fulfilling as, say, backpacking and weightlifting is for me.
