Are you worried about managing to prepare for the viva because you have work, family or a life?
When you submit, sketch out a calendar of the following three months. Show all of the days. Three months is the typical upper limit on the window between submission and the viva. Some universities aim for less, so check your institution’s expectations.
Now: cross out all of the days when you will simply be too busy or unavailable to do any viva prep. If you have holidays, block them out. If you work certain days or have other commitments then block out that time.
You’re left with all of the dates when you will probably have some time to spend on prep. This doesn’t mean spending eight hours per day in prep, just a small portion of each day typically (thirty minutes to an hour).
When you have a viva date your preparation window becomes crystal clear: you can see exactly what opportunities you have and make a real plan. Rather than start with a big list of things you could do, start with an outline of how much time you have. Work with the time that you’ve got, rather than wonder how you will squeeze everything in.