Many years ago I was studying with the Open University. During that time I bought a revision aid. The basic principle was that you wrote out all you knew about a topic immediately after learning it. The note pages were marked so that they could be referenced against a sort of calendar. The idea was that you read through your notes something like the next day, again a week later and again something like 4 weeks later.
I recall that the thinking was that the frequency set coincided with the way your brain moves stuff from short- to long-term memory.
I'm just about to start studying again and I wondered if anyone might know what the frequency for reviewing one's notes might have been.