I'd advise not to revise too early - I began to lose motivation during the most crucial days to study like three days before the actual exam.
But, honestly revising early is so much more beneficial especially with exams that require a lot of context to be remembered.
One key to studying is always revisiting previous notes. That means, you won't forget it within three weeks time. So, when I go to study I'd go over all the stuff I learnt previous such as writing what the definition is etc. Then, I'd learn something new. If I forgot something that I learned previous I'd just learn it again and so on.
After I covered all the topics that is when I move onto pass papers. I would then mark myself or a teacher to mark and go back over the topics which I got wrong.
Benefits I found:
1) I was way more relaxed and wasn't stressing myself out too much.
2) I felt as if I was actually learning the context not just memorizing it.
3) My grades were constantly improving, never failed any practice tests - this was consistent throughout the whole year.
4) I picked new information up quicker during class.
5) Actually began to enjoy studying, completely changed my attitude towards it.