When the girl's 20, and you're 28, the age gap won't seem quite as bad, but the problem is that all young people change so much in their teens. What might seem like a dream relationship to you now, could turn very sour in a couple of year's time, as you both grow and want different things out of life. I'd love to say that everything'll be great, but just be aware that as your girlfriend matures, she'll probably want to branch out and date other guys, especially once she gets to work and meets lots of new people.