There has been a recent spat of blog posts suggesting 30 (26?) is past an entrepreneur’s prime.
As an entrepreneur you are building something most people don’t understand, using a business model people think is stupid. Your competitors are throwing rocks at you, large companies are encroaching on your space, and you haven’t slept without a laptop on your lap in a long time. People telling you you’re past your prime? Just one more thing to ignore.

I personally think it has to do with a perceived personal market value curve and acceptability to risk. There is no time when smart people believe that they are undervalued than prior to when they have already established it and are compensated for it (typically the 20’s). There is also no time in a person’s life when they are more suited to take significant risks than pre-marriage, pre-kids, pre-house (typically in the 20’s). Finally, the 20’s is also when you are low on the experience and networks that will naturally advise you that luck and timing play as big a role as intelligence in hitting it big. So, with that said it doesn’t surprise me at all that many of the most successful entrepreneurs were in their 20’s. Most of these entrepreneurs went on to become CEO’s rather than serial entrepreneurs, so it also leaves open the question if these same people simply go on to lead companies if they miss their entrepreneurial sweet spot.