It’s not enough to plan your viva prep and write read my thesis: you have to spell out what you’re trying to achieve by doing that.
Don’t just pencil in a date for your mock viva: what do you want from that experience?
And you can’t simply allocate time for checking a few papers written by your external: what do you want to know from reading them?
Plan your prep so you have an idea of how and when you’ll do the work.
Set prep goals so you have a good sense of what you’re achieving and how it will help you.