I was in my mid 20's when I started getting migraines, and mine last sometimes up to 5 days, on and off. It's a cycle that occurs, not related to menstruation, and triggered (in my case) by a glass...
I was on Topomax for 18 months, and went off it because it made me very foggy headed and forgetful. (We called it Dopeymax.) Anyway, I went off it gradually, as you described, and had no problems...