I've wondered about that. One theory of mine is that she isn't more emotionally mature because she has lived this sort of dream life with talking gorillas and steampunk robots and extraterrestrial/dimensional adventures. Also, it's kind of hard to tell when some of her adventures happened, since they could have taken place at almost any time between the Sixties and now. (It would be funny to have a reunion of the interdimensional League of Teslas and half of them have grey hair and are talking about their grandkids, and the aged and unaged are all looking at each other with a mixture of pity and regret.)