The same thing happens as for traditional reading. It gets boring and the mind starts ignoring the information at some point.
PhotoReading a book more than one is when you don't get it is good also if you are studying it is often worth PhotoReading the book again just prior to each activation although not strictly necessary. Same as when you are not able to make sense of it with traditional reading you need to come back to reread it more often.
Trust your gut activate it and if activation is difficult the PhotoRead it again.
If you apply maths you will know that 3 minutes isn't a long time to PhotoRead a book but add it up PhotoRead a book 10 times that's 30 minutes with conscious comprehension at more or less zero. PhotoRead once and activate for 20 minutes and total time 27 minutes and conscious comprehension may be as complete as you need it.
Alex
