Try Something
Viva prep shouldn’t be a terrible, all-consuming task. It shouldn’t require great changes to how you do things.
It might require that you try something different though.
You might need to try a different approach to your planning to make sure you have time to get things done. You might need to try annotation-making or summary-creating to help you focus differently. Or you might need to try something as you rehearse to give you a good process for responding to questions at the viva.
If you need to try something different during viva prep then there is time to do it. Don’t wait until your viva.