https://en.m.wikipedia.org/wiki/%C4%80%C5%9Brama_(stage)
0-25y grow and study
25-50y develop your household, your family, your community and gain wealth (non-extractive, provide value).
50y-75y hand over all worldly things to the next generation, advise, teach and help those around you. Focus on your spiritual enlightenment.
75y- renounce the world and disappear into the forest as a monk / hermit.
The "Andrew Carnegie Dictum" was:
- To spend the first third of one's life getting all the education one can.
- To spend the next third making all the money one can.
- To spend the last third giving it all away for worthwhile causes.
“while in the original system presented in the early Dharmasutras the Asramas were four alternative available ways of life, neither presented as sequential nor with age recommendations.”
That's why many books contradict each other. Some books prescribe an age and order for such steps, others don't, etc. They weren't meant to be all collected, all studied, and all chosen piecemeal by one observer. But over time it has evolved into a much different thing than when it started
Edit: Not talking purely about financially giving back, but also volunteering your time.
You can more easily invest your second million than your first (Because you probably need that (Or at least a portion of that to live)
There's also no significant reason to start earlier (or later), unless you factor in dying as your stopping point, worthwhile causes aren't going anywhere