There’s lots of hours spent on a PhD, but different ranges depending on the stage you’re at:
- Five to six thousand to do a PhD.
- Twenty to thirty in prep for the viva.
- Two to three for a viva is quite common.
Each of these matters.
Your research and your talent develops over a long period; after that it doesn’t take much to get ready to defend your thesis.
And not too long at all to discuss the important things with your examiners.