In general, your inner mind will immediately go to work at bringing your conscious awareness to any material in the book which begins satisfying your need and interest for what is inside the book.
Crafting Mind Probing questions helps you build the structure alot quicker. Therefore, you will actively build more connections between your conscious and other-than-conscious mind during each activation pass.
The amount of time you should spend activating really depends on how much of your book you wish to comprehend fully. The awesome part is, you'll get there 3-5 times faster with the PhotoReading process.