Actually, some of the research they base their advice on was performed on elementary school students, and college classrooms which had poor attendance; ie, not the most engaged students. Simple things like giving elementary students an ungraded quiz right before class (to force recall) two or three times a week raised grades substantially, and a college class that switched from midterms/finals to 9 quizzes plus a final not only had higher attendance, but also had much higher grades on their finals with basically none of the students falling behind. Another experiment had young kids practice throwing beans bags into a bucket, one group alternating practice between 2 and 4 feet, and another only practicing at 3 feet. After a month or two, they were tested on throwing the bag into the bucket at 3 feet and the kids who practiced at 2 and 4 feet performed significantly better than the kids who only practiced at 3. Anyway, my point is that small, simple changes to how you study can have big implications for retention, without too much extra effort.

Sorry, I'm still reading this book right now and it's super interesting.