Coffee consumption and Migraines have something in common aside from the fact that the one can cause the other–it rarely pays to talk about how bad your habit/disease is. If you do, someone will quickly come along and you will be one-upped. Migraines range from minimal cases like mine (debilitating headaches no more than once every 2-4 weeks), all the way up to people who have them 4 times a week. Similarly, if you think I drink a lot of coffee, you should check out these folks:
Speaking as someone who starts each day with a full 12-cup pot of coffee (typically some sort of organic Peruvian), or about 1600mg of caffeine according to this handy CSPI chart, and often continues drinking the stuff till late in the afternoon, I relate.
I rarely top 600mg during one day.