SF Heroes How Old?

I received an email asking how old a Science Fiction hero is supposed to be. Of course, the answer is “old enough”, but I am thinking that in many of the best SF stories, the hero is a teenager. They say the Golden Age of Science Fiction is 14. SF heroes tend to be young because the readers are young. Even older readers like me are teenagers in heart and spirit.

Might you have some sense of the approximate age of sci-fi heroes? We have a project intended for an adult audience, and the hero is nineteen. When I think of heroes in other genres, the hero seems to be in his early thirties.
Thank you in advance for your input. Of course I would appreciate hearing from you at your earliest convenience.
Best regards,
(Name withheld on request)