Hello everyone, first-time poster here
Personally, I set this bar for myself: If I’ve recently devoured a bunch of lessons (I always try to go through them as soon as they are unlocked), I am satisfied with 80%. If I am more or less familiar with the material being reviewed, I aim for 90%. If I fail to meet these quotas, I devote some extra time on memorizing the things I got wrong.
I see a lot of people here don’t really monitor the percentage, fine by me. However, you should be aware of one aspect of Wanikani: If you scored really low, it is actually possible that you’ve made negative progress (in the “advancing through WaniKani” aspect, not “learning Japanese”).
Any item you review has to go through nine levels in total: Four levels of Apprentice, two points of Guru, and then Master, Enlightened and Burned have one level each. Every wrong answer sets the item two steps back, while every correct answer makes it move one step forward. The basic line you shouldn’t go under, in my opinion, is 66%, since that’s the point of equilibrium between your advances and setbacks (two right answers for every wrong one, the wrong answers have twice as much impact).
There are also some other factors: If the item is on the lowest level (Apprentice 1), either because it’s new or because you get it wrong often, it has nowhere to go if you get it wrong, it just stays where it is. Therefore, the point of equilibrium gets more forgiving if you are reviewing something new or troublesome. I could also factor in the time intervals for different levels: When you fall from Apprentice 3 to Apprentice 1, it’s not nearly as bad as making a mistake just when you’re about to burn an item, and falling all the way back to Guru.
Obviously, if I was to calculate the individual point of equilibrium for every set of reviews, I would go mad. So I disregard all the side factors and set 66% as a line I must never cross. If you score under this number regularly, your amount of reviews is actually going to increase over time instead of decreasing. You are bound to get swamped eventually.
Of course, it’s your WaniKani paid for with your money and you can use it however you see fit. This is just one opinion from one guy who spent too much time pouring over the mechanics of WK