Not totally, but close. There are some aspects of maturity that are age-independent. There are other aspects of maturity that can only be learned by experience, learning through and growing through the joys and pains of life. But few people actually do the work of that learning, and, according to studies of Emotional Intelligence, fewer and fewer every 10 years in America. So, the capacity to be mature, and even wise, grows with age. But examples of that are, in my experience, very rare indeed. And, meanwhile, there are stellar young men and women appearing in every generation!