When I was in Shar Yashuv I heard this idea about review ten times and I am seeing that this helps. It was how I used too do the Maharsha and Pnei Yehoshua and the other achronim like Rav Chaim of Brisk and Rav Shach I have started to see that this idea help also for Mathematics. [I do not mean to diminish the importance of fast learning also- but I think the main emphasis ought to be on lots of review and in depth learning as my son Izhak told me
