Oh dear, you don't need to know how much other guys do it! Just do whatever it isn't going to kill you and lots of guys are sexually interested by age 12 so I don't think you should be to worried.
The worst you'll get is rough skin on your hands or something
Generic answer: so long as it isn't interfering your school work or social life, yank it as much as you want. I was a twice daily man from about age 13 - 15, never did me any harm.
I know first hand (ho ho ho) that excessive masterbation can cause some rather uncomfortable abrasions. Just don't be too rough and it'll be fine. There's not really such thing as too much masturbation as long as your not too busy playing with yourself to eat.