Maths is just one of those subjects you have to be doing daily so it sticks in your long term memory or you forget the old stuff and can only remeber the thing you did last, and in the exams they exploit that they're hoping you can't remember what you did like 10 months ago. As its likely to be staring you right back in your face in the exam hall, and you won't have a clue. Theres really no such thing as cramming at the last minute when its maths.