No, wisdom and knowledge don't correlate linearly with time. Wisdom and knowledge come from insight, reflection and experience. Sure the 40 year old has most likely seen more and done more than the 20 year old, but that means nothing if he does nothing with what he has seen, and just seeing these things does not impart anyting but the most shallow definition of wisdom on a person. I've met 40 year olds far wiser than most 80 year olds, and I've meet 20 year olds far wiser than most 40 year olds. The length of time someone has been alive is not a valid excuse for dismissing what they say or the insight they've developed. Life is a subjective experience and the length of time involved means very little compared to what they've experienced and what they've gone through.