Age is a state of mind. I have met more mature 20 year olds than some of the 40+ year olds I know.
Specially when it comes to emotional maturity.
Something strikes me as a bit head-in-the-sand about people I've known who are on wife or husband number 3, and continue to say things like "I just know this person is my one true love!" <drooling ensues>.
This is obviously only one group specific example, but you get the picture.