I agree with you Pyrus, you do not outgrow metal. I remember i saw a girl after 8 years that i knew in highschool (yes, i am old) and she said, "i thought you would outgrow that!!!" and I said, no way, I will never outgrow it. I do still love Slayer and probably always will, along with other bands that I was into when I was younger.... I seem to never dislike them once I have liked them to a certain extent...maybe just tire of them or something.
My dad is still into Black Sabbath and Alice Cooper and he is 56 - it is a passion.