This will go against the grain, but I've felt rather "adult" for some time now. Occasionally I'll get the urge to throw a blue streak in my hair or something, but generally I feel like I have it together. I'm not sure if I'm just kidding myself though, because most people I talk to don't share the sentiment. Also, I have only been IDed a few times, even when buying lottery tickets and getting into snotty bars. I guess I look old? Hooray?
We seem pretty similar! I've felt this way for a while as well. I like going to work, paying the bills, doing the dishes, etc. I also rarely get carded -- waiters have been asking me if I'd like to order a drink since I was around 14! I was also always cast as the middle-aged characters in high school plays :P. I wonder if looking older has some weird relationship to this: maybe looking older causes people to treat you subtly differently, leading to more "adultlike" behavior earlier? I have 0 evidence for this though haha.
Perhaps! Yes, I was often asked, "Would you prefer the lounge tonight?" as a teen. I enjoy going to work, organizing and cleaning, reading the mail, making appointments. Also, buying furniture and landscaping gets more exciting as I age! Hmm, that's an interesting theory. My parents were always the "treat your kid as an adult" type - it was rare I felt patronized, and they usually tried to include me in their daily happenings. Were your parents the same? I imagine they would have the most influence on your behaviour and perception of yourself.