Is it possible to break Spaced Repetition?

No, I don’t believe there’s any danger of that. Specifically, I don’t think there’s any science to support that idea. (Anyone: If I’m wrong, I’d be interested to know, so if there is science to support it, please reply if you have a reference to something.)

What SRS is about – as far as I understand – is the efficiency of learning. In other words: How much stuff can you learn in a given amount of study time? (Which can potentially be an important factor, especially if there are a lot of items to learn, such as all these thousands of kanji to gain fluency in written Japanese.)

So, I believe the research that supports SRS says something like this:

  1. If you want to maximize the amount of stuff you can learn in a certain amount of study time, then you can learn the most if you spend as little time as possible on each thing you’re learning. Example with made-up, fictional numbers:. If you use method A, which requires on average 20 hours for each item learned, then in the long run, on average, if you only spend 1200 hours of time studying, you will learn about (1200 hours) / (20 hours per item) = 60 items. But if you use method B which only requires 10 hours per item, then in those same 1200 hours of study, you’ll learn about (1200 hours) / (10 hours per item) = 120 items. Therefore, method B is more efficient, and thus a better use of your time. This is because you only spend 10 hours per item, rather than 20.
    In other words, the less time spent on each item, the better.
  2. Compared to other methods, SRS – particularly when the timings are spaced so that they occur right about the time when you’re on the verge of forgetting – uses the least amount of time per item, in order to learn that item.
    (Note: I have not looked at the research myself, by the way, I’m just stating it based on my understanding from reading about the research from other people, such as WaniKani, who you could argue have a possible profit motive, but also people such as the people behind the free software Anki, who I doubt have any motive to make stuff up about it. Just saying to take what I’m saying with a grain of salt, though I have little reason to doubt it myself.)
  3. Therefore, if you want to learn the most stuff in the least amount of time, it’s best to use a method that uses the least amount of time per item, and one of those methods is SRS, specifically where you time it based on ‘just about to forget’ timing.

But if you spend more time studying an item than this minimum, I very much doubt that it will harm your learning of that item. It will just mean that you spend more time per item. And thus, in a given amount of time, you will end up on average learning fewer items. But you’ll still learn the items!

So, if you would minimally spend (made up numbers) a grand total (on average) of 10 hours per item using just the ‘just before forgetting’ rule, then in 1200 hours you could learn 120 items. But if you augment that with an additional 2 hours per item doing extra reviews (e.g. the Extra Study feature), then instead of each item taking 10 hours, it will take 10 + 2 = 12 hours, and as a result within those same 1200 hours, you’ll only be able to learn 1200 / 12 = 100 item. Since 100 is less than 120, then on average you are being less efficient with your time. But you’ll still eventually learn all the items. It will just take a bit longer.

In the end, IMHO, being maximally efficient with your time spent learning Kanji (and Japanese in general) is one consideration. But it’s not the only consideration. And how important efficiency is will depend from person to person.

Personally, I spend more than the minimal time learning kanji because I happen to be a bit of a perfectionist (which is not actually a good thing, IMO, it’s just part of my psychological make-up), and so I feel a certain ‘uneasiness’ with learning only to the point that I’m ‘just about to forget’. My perfectionism means that I feel like, “Well, I don’t want to be on the verge of forgetting. I ‘need’ to know it solidly,” even if that means it takes me on average longer to learn the items.

Indeed, that’s a big reason why I got the lifetime subscription from the get go. I knew at the beginning that I would end up wanting to use WaniKani for at least a few years. And these days I know that actually it will be for several years. But since I invested in lifetime, I don’t have to think about being the most ‘efficient’ in learning. I can instead take my time.

It even got to the point where I joined in on the forum thread celebrating ‘going slow and steady’ at :durtle_hello: Let’s Durtle the Scenic Route :turtle:.

So, don’t worry about ‘sabotaging’ your own learning by using something like Extra Study. At worst, you’ll spend a bit more time studying. But on the other hand, you’ll probably feel more confident in what you’ve learned as you go along. It really just depends on what your own personal priorities are for learning Japanese. Fast-fast-fast? Slow-and-steady? Or somewhere in between?