I knew a couple who got to level 75 in like, 5 months. It was insane. I've been playing for 3 years and the highest level character I have is level 69. BUT, I don't play that much. In fact, I don't think I've logged on in like a month. Not by choice, but just things got in the way of being able to play. It really depends on how much you play, how lucky you are with your parties, etc.