Hi there,
I saw your earlier post on my "gift for the rabbi" thread.
I think conversion processes can take any amount of time. I had a friend whose conversion took only 4 months. I've heard of them taking 2+ years.
My conversion started March of last year (right before passover), and will basically have taken 11 months. I had study sessions with the rabbi twice a month, and once a week for the past six weeks.
I'm not sure what type of conversion you are having though. Mine is reform, and I think if your is conservative/orthodox, it might take longer. Have you started "officially"? If you have been living "Jewish-ly" for the past year, and your wedding is 18 months away, I can't see why you wouldn't be converted in time. But I guess it is a decision up to the rabbi.
Basically my rabbi wanted me to:
-have a grasp on Jewish holidays/festivals and life cycle events
-be aware of history of anti-semitism and effects today
-learn about history of Israel and Israeli relations today
-live a Jewish life (Shabbat, going to shul, being involved in synagogue community)
keep me posted on what your rabbi tells you...good luck!