Asking whether you'll jump or not, is always the wrong question. If you're asking yourself that question, you're probably not an entrepreneur. Most entrepreneurs that are successful have multiple previous startups and have always made the jump early and frequently (Jobs and Wozniak with their illegal long distance calling hack, Zuckerberg with a collaborative fitering music sharing app in high school, Aaron (Mint.com) with his multiple startups back in college, etc). Doing every progressive experience gets you used to doing another startup and making you comfortable for the jump. Doing a startup isn't like rolling the dice and seeing if you can win the lottery, it's more of a compulsion.

There was a blog entry :

http://www.avc.com/a_vc/2008/04/ten-questions-a.html "Is there an ideal age for an entrepreneur? No, although most start at a young age since they don't belong in big companies. But once an entrepreneur always an entrepreneur. We've got one entrepreneur in our portfolio who is approaching 60 and working on his fourth company."