900 Reviews Due: How to Clear a Spaced Repetition Backlog

It happens to everyone who uses spaced repetition for more than a few months. A holiday, a flu, a deadline at work, and one morning the number on the screen says 912. You close the app. The next day it says 947. A week later you have stopped opening it, and three months of German are quietly sliding away.

The pile is the most common reason people quit a method that was working. It is also much less serious than it looks, and there is a calm, mechanical way out that takes about two weeks.

What the number really means

Three facts take the fear out of it.

Most of those cards you still know. A card that was due ten days ago and that you can still answer has just proved it could survive a longer gap than planned. You get it right and it jumps far into the future. Only a part of the pile is truly lost, and the proportion is smaller than you expect, usually a fifth to a third after a month away.

The pile does not grow as fast as it did. While you were away, each card fell due once. It did not multiply. The number rises every day only because cards that were not yet due are reaching their dates.

Late reviews are not wasted reviews. Reviewing a card late and getting it right is, if anything, stronger evidence of a solid memory than getting it right on time.

So 900 due cards is not 900 forgotten words. It is perhaps four to six hours of work, and it does not have to happen today.

Three things not to do

• Do not reset the deck. Starting from zero throws away the one valuable thing you have, which is the history of the words you still know. You would spend two months re-learning words that needed one review.
• Do not grind it in one night. After about forty minutes, accuracy drops and you start pressing "correct" to make the number move. Those cards then get long intervals they have not earned, and the problem returns in a month, hidden.
• Do not keep adding new words. Every new card adds eight to ten future reviews to a system that is already over capacity.

The plan

Step 1: set new cards to zero

Today, before anything else. In Anki, set "new cards per day" to 0 in the deck options. In merke.me, set "new per day" to 0 for each active deck, or simply do not start lessons. Nothing else in this plan works while new material is still coming in.

Step 2: choose a daily number you can keep

Not a heroic number. A boring one. Take what you were doing before the break and add half: if you did 80 reviews a day, do 120. In time, that is fifteen to twenty-five minutes.

Split it. Two sessions of ten minutes clear more cards, with better accuracy, than one of twenty.

Step 3: do them in a sensible order

If your tool lets you choose, there are two reasonable orders.

• Shortest intervals first. Cards that were at a one or two day interval are young and fragile; they are the ones you will lose if they wait another week. Old cards at a two-month interval can wait a few more days without harm.
• Most overdue first. Simple, and it guarantees nothing waits forever.

In Anki, a filtered deck does this: search is:due, limit it to your daily number, and order by "relative overdueness". Rebuild it each day. If that sounds fiddly, ignore the order and just do your daily number. Consistency matters more than sequence.

Step 4: answer honestly

During a backlog the temptation is to be generous: "I sort of knew it." A wrong answer feels like making the pile bigger. It is not. A wrong answer puts the card back on short intervals, where it gets repaired. A false "correct" sends a forgotten word two months away.

Step 5: bring new words back slowly

When the due count is back to a normal day's worth, restart new cards at half your old number. A week later, go back to the full number, or stay at half if the old pace was what caused the gap.

How long it takes

A rough guide, assuming your normal daily load before the break was about 80 reviews and you now do 120 to 150 a day.

The pile clears faster than simple division suggests, because every card you answer correctly leaves for weeks or months. The first days are the worst. Around the halfway point the number starts dropping quickly, and that is a good moment to notice that the plan is working.

After a very long break

Six months or a year away is a different situation. Do not open the main deck and stare at 4,000 due cards.

• Old cards with long intervals: review them in batches of 100 a day. A surprising share will still be there.
• Everything that was young when you stopped: in Anki, select those cards and use "Reset" (called "Forget" in older versions) to return them to new. They were never properly learned, and they will go faster the second time.
• Give yourself a month before judging how much is left. German that was learned once comes back much faster than it went in.

Why the pile formed, and how to prevent the next one

A backlog is almost never caused by the break itself. It is caused by running at full capacity before the break, so that a few missed days were enough to tip it over.

• Run at 70 percent. If you have 30 minutes on a good day, plan for 20. The spare capacity absorbs a bad week.
• Reviews before new words, every day. New words are optional. Reviews are the product.
• Keep the youngest stage small. In WaniKani terms, fewer than about 100 items in Apprentice. If the early stage is swelling, pause new material for a few days.
• Pause before you leave, not after. Stop new cards a week before a holiday. The review load is noticeably lighter when you get back.
• Use a pause feature if you have one. Anki has no real vacation mode. merke.me does: you set the days you are away, every due date in that window moves back by the length of the break, and your streak is not broken. You come back to the same queue you left.
• Two minutes beat zero. On a bad day, do ten cards. The habit survives, and a habit that survives is worth more than any single session.

The right daily number, with the arithmetic, is in how many German words per day.

When a few cards make up half the pile

Clearing a backlog often shows something else: the same forty cards fail again and again, while the other 860 are fine. Those are not a backlog problem. They are cards with a defect - a twin word, a missing article, four meanings on one card - and they will keep failing at any pace. Suspend them while you clear the pile, then repair them one by one with this guide to stubborn words.

If the method itself feels wrong

Sometimes the pile is a message. If you came back, cleared it, and felt nothing but dread, the load was too high for the life you have. Halve the number of new words for good. Ten minutes a day that you do for two years will take you to B2. Forty minutes a day that you do for six weeks will not.

And reviews are only one part of learning German. If flashcards have become the whole of it, add something you would do for pleasure: a series, a podcast, a book at your level. The words you review are meant to be met again in the wild, and meeting them there is what makes the reviews feel worth doing. A balanced week is sketched in the 30-minute German study plan.

If you are looking for a system with the pause built in and the daily numbers easy to turn down, the decks in merke.me each have their own "new per day" setting, and the first 100 words and 30 grammar points are free.