You might need to set some for your viva prep. They’re arbitrary in the sense that they’re not fixed by a strict process, but by your needs, your circumstances. For example, there isn’t a deadline for when you must have read your thesis, or you have to have a mock viva. Annotating your thesis can be really valuable, and you can do it whenever you need to. It helps not to do it on the morning of your viva, of course.
It’s useful to think about your prep ahead of time and set milestones for yourself. They’re just for you, to help your prep be as stress-free as possible and guide you into feeling ready for the challenge of your viva. Look ahead to the time around your viva and consider what milestones can help your personal journey to being ready.