Jack didn't let his chronological age dictate his behavior, and neither should the rest of us. There are lots of examples in On The Road and The Dharma Bums where a character displays what society would probably label "immature behavior" or "juvenile antics."
Like sunbathing naked. Or sneaking aboard an abandoned boat. Or pissing off the back of a moving truck. Or dancing in public. Or inventing and playing a game. Or staying up all night.
If you want to do it, do it. Don't let age stop you. Stay young at heart.
Youth is not properly definable by age. It is a spirit of daring, creating, asserting life, and openly relating to the world.
Well said, Malcolm.