How long does it take to "Forget" a subject for exams? I'm interested in studying a subject for exams, completing the basic studies a few weeks before the actual exam day. If I study it "deeply", meaning I have an understanding of it that is beyond the surface and I actually understand the meaning of the underlying math, will I be able to hold that knowledge for exam day? In general, do you think you can hold the knowledge for a subject you will be tested on - or you need to use it on your work - weeks after studying it? And if yes, what is the process that you should follow in order to do it properly?