There aren't any hard and fast rules with one's willingness to learn and grow. The point about this statement is that when we are young we think we know more than we actually do ("we don't know what we don't know and we don't care that we don't know). As we get older and garner more experiences we come to realize that maybe those who were trying to give direction to our lives really did have more to offer than we thought they did. The important thing to remember is not how many years we have lived but how much learning we have put into our years.
True, life is a journey and we should gain some wisdom along the way or the whole trip was a waste.