One of the lessons I learned from my son Izhaak [aka nachman] i learning in depth. And I have been trying to concentrate on that. But I can see that in math and physics  every chapter builds on the previous chapter. Thus just to review one chapter a lot of times does not help. so I reached a sort of compromise of lot of review on one chapter but also go back to all the previous one. --every day one chapter back. But also to do "bekiut" to have some sessions of just saying the words in order and going forward.