True maturity brings a sexy level of confidence. I don't care how "grown up" a teen or 20-something lady "appears" it's been my experience that inside is a young girl that's still unsure of herself and striving to shake off the last vestige of self-consciousness.
Women over 30 are usually there. They've had enough "been there, done that" moments and actually lived a life that their self-confidence is firm and the sexualty they express comes from years of learning and experience. I swore off "little girls" after an uninpsired blowjob that consisted of her basically just dropping and lifting her open mouth. Not what you call "exciting." Give me an older woman that's had enough of them in her mouth to have an understanding of which buttons to punch when you're with a man.
I would hope it's the same thing for women in terms of older men but I digress!