Should I be worried about my boyfriend going to college?

I trust him, I really do. He's like my best friend and I don't think I believe he'd do anything to hurt me. I'm not afraid of him cheating so much (in fact, I find the idea pretty ridiculous), but I am scared he'll fall for someone else or "grow out of me" or whatever. We've been together almost a year, and in the fall he's going off to college an hour away, while I still have two years left of high school. He says there's nothing to worry about, and he's never given me any reason not to trust him or his feelings for me (he's been the best boyfriend I could have imagined). Still, he means so much to me that I can't help but be scared.