This is referenced by Andy Matuschak in How to write good prompts. Using spaced repetition to create understanding.

When to use Anki

I find Anki works much better when used in service to some personal creative project.

Anki useful, but it’s definitely most useful in new areas (…) One common pattern is that people think they’re getting stuck on esoteric, complex issues. But when you dig down it turns out they’re having a hard time with basic notation and terminology.

Avoid completionism:

One caution is with books: reading an entire book is a big commitment, and adding Anki questions regularly can slow you down a lot. It’s worth keeping this in mind when deciding how much to Ankify. Sometimes a book is so dense with great material that it’s worth taking the time to add lots of questions. But unmindfully Ankifying everything in sight is a bad habit, one I’ve occasionally fallen into.…

If you feel you could easily find something more rewarding to read, switch over. It’s worth deliberately practicing such switches, to avoid building a counter-productive habit of completionism in your reading. It’s nearly always possible to read deeper into a paper, but that doesn’t mean you can’t easily be getting more value elsewhere.

Again, as in many places (such as Range), it won’t look like you are truly learning:

Many experiments also try to assess participants’ perception of the effectiveness of massed practice versus distributed practice. Remarkably, they often believe that massed practice is more effective, despite the fact that it is reliably outperformed by distributed practice.