At what age do men really grow up?

My father once told me that the true responsibility of "manhood" doesn't set in til around 40. He said men go thorough all these stages where everything is more important to them than the things that count. (family, fidelity, finances, faithfulness, faith...etc) That's a little discouraging.. I have a friend that is struggling with her 3 + spouse, whom she thought was on his "grown man", acting as if he is reliving his teenage years. "The guys" seem to dictate his every action and he seems to rely heavily on what they think. He doesn't communicate well and feels its his way or NO WAY, and though he talks a good game about his future, his current actions don't match his overall future financial plans. Whats up with this? In talking to co-workers and other friends, I realize many women have this problem. Are they all reading from the same book or what?