That's a great point. In my experience, this is what makes bootstrapping your own startup the most practical option if you are older and have more commitments, because who wants to give money to someone who can only commit 10 or less hours a week to something?

Maybe I'm wrong about this because I've never actually tried to get funding for anything, but the ycombinator program definitely seems that way. My wife certainly isn't going to agree to move to SF and live on that kind of money. I'd have to have another income stream or a lot of money in the bank.

I'd be curious to know how people have gotten around this.

I'd agree - it's merely the risk-return equation that needs to be considered at a higher level once your over the "tween" period. There is absolutely nothing stopping you go forth and conquer - however, the probability that you have an inordinate number of external commitments [social and financial] are where the ability to be nimbal become more apparent.

Stopping work and having what ajg1977 states - "Mortgage, day care, insurance, kid commitments etc" - is the battle. Many successful startups have an average "age" of around 26 which seem to be [from some Y-Combinator article I read] the age when startups succeed for a whole raft of factors [age, martial status, flexibility, financial security, maturity etc etc] - there's always an exception to the rule however.

If you >30 - nothing's stopping you but yourself. The question often answers itself however - most >30 stop themselves due to externalities.

*but best of luck :P

Actually those commitments helping me to make better decisions on when/how/whom/what start a new startup. In my twenties(I am 33 now) I used to jump right in because the idea was interesting and I had an excuse to stay up all night to code on something. Now I make sure the idea or the project is worth to cut into family time.