Viva prep can take between twenty and thirty hours of work when you consider all of the tasks that could be involved. In the time leading up to your viva, thirty minutes to an hour per day of viva prep could be enough to help you get ready.
It all depends on when you start and how much you need to do.
Start your prep with three weeks to go and spend thirty minutes or an hour each day doing something to help yourself and you’ll have no problem in making things right for the viva. You can take days off or find time to invest an extra hour maybe and the necessary work will seem to be done in no time.
By choice or inactivity you might start your prep with a few days to go. In this case you might have to spend six or seven hours per day on viva prep. It’s not ideal, but it might just be what you have to do.
I think it’s far better to plan for the situation, just a little. Prep for your prep. Take some time to figure out how to make getting ready as unhurried and as stress-free as possible.
You have to put in the hours to be ready for the viva – but you can decide how and when you invest those hours.