Hello,
I would advice that you start in January and slowly increase the amount of revision leading up to the exams.
I would advise you regularly go over your notes and do lots of practice questions from memory. This is active recall which is the most effective way to learn and memorise content. Nearer the time you should also do your own mock exams in your own time under complete exam conditions.
You could also do quizzes on platforms like Kahoot or Quizizz as these can be fun ways to revise. Seneca Learning is a very good revision platform for GCSE and A Level and on the premium platform it will tell you what to revise and when based on psychology, specifically the Ebbinghaus Forgetting Curve.
In summary, the key thing is to continuously go over the content, if you want to learn about the psychological evidence behind this research Atkinson and Shiffrin's Multi-Store Model of Memory.
If you have any further questions please do let me know.
Charlie
Law LLB Student