From prior experience with a massive backlog due to a vacation with SRS systems in general (specifically Anki, not WK, but it’s essentially the same thing) for another language, I don’t recommend tackling them all at once because, as you’ve already noticed, you are going to miss a lot of them since it’s already been longer than the intended interval which means you will have mostly forgot many of them. That, in turn, means you’ll just end up with another massive barrage of reviews in a day or two and you will miss a bunch of those too which causes them to come back again in another day or two after that and so on.
This very thing nearly made me quit using Anki altogether back in the day until I changed strategy to the following which is what I personally found is the good way to tackle backlogs:
- Stop doing new lessons/cards until your backlog is caught up
- Do about 25-35% more reviews per day than the number of reviews you were doing prior to accumulating the backlog while ensuring that you’re doing enough for your daily reviews to trend down. It might even take a slightly higher percentage for the first few days depending on just how long the backlog has been accumulating (and hence how much you’ve forgotten).
- For the ones that you can almost remember, don’t really worry about studying them again too much, since you’ll very likely be able to recall them on the next SRS without too much issue.
- For the ones that seem to be completely gone as if you had never even seen them to begin with, take the time to study them a bit, as if you were redoing the lesson.
For a concrete example, let’s say you typically were doing 100 reviews per day prior to the backlog and now have have a backlog of 700 reviews. Let’s also say that you still have about 50 more reviews from before coming due every day. It should typically be much less because of the period you weren’t doing new lessons which led to the backlog.
The first day you would do something like 100*1.35 = 135 reviews. That would lower the review count down 565, but you’ll probably miss about 54 of those 135 reviews (aka 40%) which will come back the next day (or two) along with the other 50 coming due for a total of 669.
Then, on day 2, you would do another 135 reviews lowering the count down to 534, but again, you’ll probably miss roughly 40% again, so add that 54 back along with the other 50 coming due for a total of 638.
That would continue for another day or two and then from that point, you’ll start missing less because many of the reviews coming up will be the ones you recently missed and will be on the “correct” interval again, so the number of reviews will start going down more quickly until you reach 0. It’ll probably take about a week.