While viva prep depends a lot on the person, their research and their circumstances, there is one quality I wish for every PhD candidate’s prep: I would want it to be unrushed.
No rush. Pressure can be useful as a motivator for some but I don’t think stress is ever helpful.
Plan your prep. Give yourself the luxury of time and space to do the work well.
No rush, no hurry, less stress, less fuss.