Data/results from it would be near useless unless you were able to question only people with zero-responsibility (ie no family, commitments) and equal risk.
Not necessarily - depends on your goal in such a study. If you were looking to see the impact of age and age alone, sure that'd be tough to control for with all the added factors. However, startups don't occur in a vacuum and I think it'd be interesting to see some comparisons without worrying about age as the only factor.
Most research points to mid/late 30's as the peak of technological breakthroughs (largely determined by age of Nobel winning work). I'd actually be somewhat surprised if successful company founders weren't largely distributed around that same range.
