I would argue that the mental differences between a 28 and 40 year old are much less, however.

I'd ask you to cite your reasoning. The average age of first child in western societies is almost hitting the 30 year old mark, so I'd argue that (in western societies at least) there is a dramatic mental difference between those in their mid 20's over those in their mid-thirties.

How does the fact that the average age of first child in western societies hitting the 30 year old mark support the argument that there is a dramatic mental difference between those in their mid-20s and those in their mid-30s?

Maybe I don't have enough perspective. I'm only 23, and maybe I will think that I'm dramatically different when I'm 40. Right now, it just doesn't seem like it. Then again, most teenagers think the same way about being 23 (me included).

Heh - I'm dramatically different from the 23-year-old me and I'm only 34.

(And thank god, because the 23-year-old me was both insufferably stupid and didn't know it.)

(Now at least I know it.)

Remind me to ask you what you think 11 years later.

At least we know there's a nonzero probability that your perceived insufferable stupidity is monotonically decreasing. :-)

I think most cultures consider their elders to have much much more wisdom than regular men.

Forty years old is an elder?

Not that per se, but wisdom increases with experience and age is a big factor in having experience. A 50 year old person is likely to have experienced much more than a 30 year old. So it's natural that you will find 16 year olds lacking in experience compared to say 28 year olds.

I'd say 28 year old entrepreneurs have very different risk profiles than 40 year olds, and therefore think very differently.