Am I wrong hanging out with people 3 to 4 years older than me?

Well I'm 15 but all my friends are 18 and 19 and I prefer older friends because the people in my class are to immature and they like childish stuff such as Video Games and Pop Music. I'm 15 but I look about 18 or 19 and I go to the pub with my friends all the time and I have no problem getting served and I go to Heavy Metal gigs as well because heavy metal is the best form of music ever created as well as Extreme Metal. I have never been into Video Games because I'm to mature for that and I have never owned any Nintnedo's,Playstation's or Xbox's or any of that sh*t. Instead I listen to music or surf the web and I probably would of liked Video Games when I was younger but now I'm to mature for that sh*t. I also have a girlfriend who is 19 and we have had sex to and we have a good steady relationship. Am I growing up to fast?