I've activated books after only one photoread. Works just as well photoreading a book a couple of times. In particular textbooks for learning. Each time you photoread you can approach it with a different question in mind. A different focus and as a reminder for your ultimate goal... e.g. 'to successfully understand and use the information contained in the book'.
One reason for photoreading a textbook more than once is, it keeps it in the minds high priority list of what the current project is as a focus toward a goal. Keeping it to the front of the pile 
Repeating the photoreading process also helps the conscious mind to be aware of the information being presented to it. Keeping the conscious mind on track for activating and understanding the text more than placing the information into the inner mind is the real purpose of photoreading text more than once. All the information is there from the first time that you photoread, just doing it again is to help your conscious mind realise your goal.
Alex
