Well, the majority of my friends are between 19 and 26 and are often newlyweds and even sometimes have the cutest kids ever .
But maturity is not a question of age . One of my best , level-headed and compassionate gaian friend is 15 years -old. Well, at least she does sound more mature than the 18 years-old you.
And why would you have something against 'kiddies ' ? I mean , they ARE human beings and often have many lots interesting things to say or a lot of creativity and aspiration . Except if you are taking Gaia for a dating site , which it is not.
And as stated by previous Gaians , it depends where you go : the flash spaces and some parts of Chatterbox have a bigger ratio of young teens while the GD or hobby-oriented forums have older people . I know from the WG being my home that almost everyone there is over 20 except for I and three others.