Spaced Repetition as a Ratchet
For the last couple of years I have been using spaced repetition to revise and learn a variety of topics - linear algebra, probability, some ML concepts and a few programming libraries amongst other things. I’ve read quite a few posts and articles about the effectiveness of spaced repetition as a learning tool, but from memory none of them highlight the “ratchet” effect that in my opinion is the main strength of the technique.
A ratchet enables movement in one direction but prevents it in the opposite direction. Spaced repetition ensures that any forward progress that you make is retained, and prevents the backsliding that is so common in traditional studying methods.
At university my usual studying pattern was to spend 3-4 hours at a time on a particular topic, revising material and doing problems. Picking the same topic back up after a few days (or longer), the first hour or so of the session would usually be spent reminding myself of what I'd previously gone over.
Now my time is significantly more limited and so it is very rare to even get an hour to sit down and focus without interruptions. Trying to learn a new topic in scattered 20-30 minute sessions would be fruitless if I had to spend the first half of the time relearning what I'd gone over previously. However, if I use that half an hour to make 10 flashcards whilst working through a few pages of a textbook then I can review those flashcards on my phone in free moments over the next couple of days, and when I get back to the textbook I can immediately pick up from where I left off rather than wasting precious time reviewing the previous few pages to get my bearings
I have used this method to successfully work through complex topics (e.g. a textbook on convex optimisation) in short snatches of available time over periods of several months. The daily review process of spaced repetition means that the material is always fresh, and I retain the information significantly better than I used to. I would estimate this technique has been a 2-3x multiplier on my learning efficiency.
I would highly recommend this method to other time-crunched people looking to learn complex new subjects.