I was almost offended, at 29, to be called an oldie. *sigh*
Then, when you said you were a teen, I understood. For someone your age, thinking of being nearly 30 is like me imagining I'm 80! 
Davinagirl3 has a great point. Many people 'peak' around 18 years old and spend the rest of their lives wishing for that feeling of popularity and importance they once had. For me, life really began after I got out of the weird microcosm of high school.
Us old folks aren't all bad - some of us have sage advice to give, though others are admittedly rather cantankerous and unpleasant. 