Before submission, you could always…
- …read one more paper.
- …do one more test.
- …ask one more question.
- …check one more thing
- …have one more meeting.
It won’t take much to prepare for the viva, but however much you do, you could always…
- …read your thesis one more time.
- …check one more paper by your external.
- …have one more conversation with a friend.
- …write one more summary.
- …worry one more time about what you might be asked.
There’s always more you could do, at every stage of the PhD. You don’t necessarily need to do that though. Instead, think about where you are, and think about what enough means for that stage.
The viva is one more day you get to show up and show what you can do before you’re finished.
Make the most of it.