It took me about 12 weeks to prepare myself to be ready.
I started with the Mike Griffts book and went carefully through each section. Mike did a great job by condensing the stuff and also preparing some test questions for each section.
But afterwards I wasnt really motivated to repeat the stuff again and dive into serveral unclear items. That was the time when the prepcast comes into the play.
The questions are well prepared and similar as in the real examination. But the real value of this simulation for me was to keep my motivation high throughout the whole time.
My advice: Do the simulation tests as often you can and check the right (and wrong!) answers against the hints and the book.
Good Luck! Hendrik