The importance of 5 months of preparation cannot be equated to one day revision before exams. The one day revision is way more important. The reason is if during the one day, you waste even an hour, it can change your confidence level and eventually your overall preparations.
The key is to sleep well for 7 hours, plan well for those 20 hours with proper prioritizing and notes. Say, you have planned only 8 hours for the first 6 chapters. It has taken you 9 hours to complete. You should not panic at this point since as per the planner, you are completing the examples along with. Also, you have already revised the most important 6 chapters in just 9 hours. This will give you some surety and confidence for further preparation and for the exams.
We suggest that you complete the revision of the most important chapters in those 6 hours after you come from the exam hall. This will relieve you from the heavy burden of completing many chapters on the next day.