I'm interested in learning about and implementing study aids, boons, leads, pointers, ..., preferably those proven through research. I'm regardful of questions such as How to set a realistic deadline for a study task when you aren't familiar with the subject?, How to study efficiently few days before the exams [considering that one hasn't throughly studied any subject by now]?; though I'm seeking more specific, categorical answers. Please feel free to emend or dilate upon this or dilate. I tender some example questions:
How many subjects should be studied during a day? Per contra, is it more productive to devote a day to a subject? For example, what interval of spaced repetition befits math?
What's the optimal number of hours of study per day?
Does it veritably help to take days off from studying? If so, how many? How often? Moreover, should students halt/suspend study for a longer period, on the order of a "vacation"?