Thomas Jefferson was quite young when he wrote the Declaration of Independence. On the other end of the scale, Benjamin Franklin was quite elderly, yet he went through the period of declaring independence, the war, and the Constitutional Convention. He lived just long enough to see the Constitution ratified.
I think Thomas Jefferson was only 35 whe he wrote the Declaration of Independance.
Age is a strange things some people at 40 are older than some at 70 and it is not just to do with health.
I get the impression some people think they ought to behave a certain way and think a certain way once they over 40.