It definitely helps a lot for axioms, basic definitions, basic theorems, distribution functions and for things you "get wrong every time" etc., but everything beyond that it's inferior to exercises. As an example: I remember learning set theory and the subset relations of the number sets much faster than anyone else in my class.
One hack I've been using is making cards like "How to solve exercise X on Book Y, page Z?".
For me, doing a lot of exercises only once has worked worse than doing some key exercises more than once, and by using spaced repetition software (Anki, Flashcards Deluxe, etc) you can leverage its systems to get an optimized "schedule" for solving/revisiting exercises for math, physics, etc, so you don't have to worry about timing issues (like how many sessions of studying, and how long/frequent they should be).
