This seems to be a very big issue for students, when should you start revising? they don't want to revise too early or else they will burn out, and not too late and not have enough time to revise everything. So when is the best time to revise?
Honestly start now, being consistent and doing a bit everyday will be helpful in the long run as the information will be stored in your long term memory. Also, when it comes to exam season you won't feel stressed or overwhelmed as you are already prepared and just need to do practice papers to make sure your exam techniques are refined.
Being calm is very important when taking exams as it allows you to have a clear mind and enables you to think better!