Start at least 2 months before the exam (so about mid-October), after you’ve finished your first reading and review of the entire curriculum.
Over the next 2 months you should periodically update your notes (as you find mistakes from doing mocks and practice questions) and review them. If you’ve done every mock, all the BBs and EOCs, and online topic tests 2-3 times, and can remember your notes (which should be condensed into one notebook), you’ll be in good shape.
It might seem overkill for level 1, but this level of diligence will also be good practice for your preparation for level 2 and level 3, if you get that far.