Well,I PR boks or notes 3-5 times at one time(relevant to the number of pages),And i think that it helps,I feel that i really remember the textbooks more and trying to memorise anything is a lot easier,But put in mind if u haven't tried soft gaze exercises before this will tense ur eyes (Sometimes it happen to me while PRing or doing the exercise),So don't PR anything to much 2-3 times is good enough to satisfy ur conscious mind .