The key is to not get stuck in the non-entrepreneurial world for so long that you forget how to be entrepreneurial.

I wonder what is the correlation between people that start their companies after 30 and their long-term success rate...

To me, I feel like after my 4-5 yrs of work ex, I am more prepared to handle any situation and also have built a list of people to reach out to for guidance, help and just PR. Its important to have that under your belt so you can smoothly transition.