its not my style right now. so i wouldn't wear it as an adult unless its like i'm stepping out for a quick second and being casual. or if i'm wearing at pajamas. but if it goes with your look you can wear it at whatever age you want. but for me i wouldn't have worn that anytime after middle school. cause during high school my style went more sophisticated.
That depends on how you look, do you look young or right at your age? If you look young and are trying to look older than don't wear this shirt. otherwise go right ahead!