It depends on your circumstances, and specifically whether (a) running the company is what you most want to spend your time on and (b) whether you want liquidity and diversification.
I didn't want to spend my life running Viaweb, and I did want liquidity and diversification, so selling it made me very happy.
"running the company" is much much different than "running your own company".
After I sold I had to stay for 3 months for transition. That was brutal. I couldn't have been unhappier and felt that those three months would have been super valuable to get a head start on the next thing (which took about 5 years..)
If I did it again I would make sure that the consulting time was on an "as needed basis" and not 9 to 5 or any fixed period.
One interesting thing though happened. After the consulting was over I went on a ski trip. I was called during the trip because they had some system problems. Solving those problems I really enjoyed doing and I continued to do that free of charge for the next year or two. My payback was simply hearing the appreciation (this was back in dial into system by 2400 baud modem days.)
"Founders who are thinking of selling" is a clue that it's after YC has invested. But obviously it's no big secret since he's posting it on a public forum.
I didn't want to spend my life running Viaweb, and I did want liquidity and diversification, so selling it made me very happy.