What is a good point in a relationship to get engaged (months, years, etc)?

I've been in a serious relationship for almost a year and a half now, and I am SOOOO much in love with my man! We talk about marriage a lot, and how both of us are ready. He's graduating w/his masters from college in may, and I still have 1 more year left. He's going to get a job while i'm still in school. Do you think there's a chance he'll be proposing anytime soon? I've been hinting for Christmas, but I'm not expecting anything.