I'm 40+ and find his advice quite good and spot on. Reading and thinking on such matters, and hanging around with wise man (he surely does) will make you grow wiser faster. I don't think there's a speed limit on anything if we're talking about humans. There will always be high achievers like Sam, his career shows it. I learned not to ignore them regardless of age and feel good about it.
You barely become a real adult at 30 (before you're just a "legal" adult) and there's a lot more experience needed to advise people about their lives.
Oh and fwiw, I'm 37 and still don't feel qualified to teach people about their lives.