Yes - five.
Why is this important to you as a speaker??
Your keynote should have a book version. I know that sounds overwhelming - I'm not asking you to write a 250 page full-fledged memoir or novel (unless you want to *ahem*. ). What I am saying is that if you really want your keynote to change lives, your listeners will want to take a piece of it home.
Do you have your book/ebook done?