For in-service performance and long term learning in general, I don't think cramming will make much difference. Maybe a few percentage points. The people that cram and pass almost certainly would have passed without it.
Instead, I highly recommend something sustainable, like 5-10 ROSH questions a day. Actually read and try to learn from the answers. Quick, 10-15 minutes of your time. By the end of the year you will have done thousands of questions and will have had better knowledge retention than trying to cram a thousand questions in say a month.
But that's not why you are here, you are here because you are looking for something short term. I'd still do questions. A good free resource of high yield facts is EM foundations board review comprehensive packet. Its a systems-based Q+A of high yield facts. It's extensive, but free and an excellent resource. There's also a quizlet version for those that prefer that format.