How do you know when you have studied enough today?

Most review apps cannot answer this, and it is not an oversight. If the queue never empties, the session never ends, and the decision about when to stop gets handed back to you — every single day, while you are tired and your judgement is worst.

That is the real problem with an infinite queue. It is not that it is too much work. It is that it converts a scheduling question, which a computer can answer, into a willpower question, which you have to win again tomorrow.

Why "just do more" is the wrong instinct

Spaced repetition already decides how much is due. The whole point of the schedule is that a card comes back at the moment it is about to fade; reviewing it earlier is not a bonus, it is spending today's time to buy nothing. If you finish what is due and then keep going, you are reviewing cards that were not ready, which teaches you slightly less per minute and makes tomorrow's queue no smaller.

So "enough" already has a definition: what was due today. The difficulty is not knowing the answer, it is having the answer visible and having the tool respect it.

A stopping rule you can actually hold

Three that work, in rough order of how well they survive a bad week:

Finish what was due, then stop. The cleanest rule, and the only one that lines up with what the algorithm is doing. If your app shows a due count, that count is your day's work. Reaching zero is a real finish line, not an arbitrary one.

Cap the time, not the cards. If the due count is enormous — a backlog, or a deck someone else built — a fixed twenty or thirty minutes is more honest than pretending you will clear it. The cards will still be there and the schedule will absorb the delay. What will not survive is you doing ninety minutes once and then avoiding the app for a week.

Cap new cards before you cap reviews. Every new card you add today becomes several reviews later this month. If the load is too high, the lever is the intake, not the review. Turning new cards down to zero for a few days is the single most effective thing you can do to a queue that has got away from you, and almost nobody reaches for it first.

What does not work is "study until I feel done". That feeling arrives either far too early or long after the useful part has stopped, and it is heavily correlated with how the rest of your day went.

The part nobody mentions: failed cards

Any honest stopping rule has to say what happens to a card you got wrong. In most systems it comes back in the same session — that is the correct behaviour, because a card you just failed has not been learned and scheduling it for tomorrow would be a lie.

Which means "finish the queue" can take longer than the initial count suggested, and that is not a bug. It also means you cannot shorten a session by pressing again on everything; that makes it longer. If you need to stop before the queue is empty, stop — do not try to rate your way out.

How Quat does it

Quat is an iPhone and iPad app I make, and this is one of two behaviours it was built around, so treat this as a description from an interested party.

A session ends when the day's cards are done, and it ends properly: the screen changes, and there is nothing left to press. There is no "keep going" button offering you cards that were not due, because reviewing those buys nothing.

The mechanism is worth stating exactly, because "the session ends" is the kind of phrase every app would claim. The queue is taken as a snapshot when the session starts. It cannot grow while you are in it. Nothing you do during a session — no card you fail, no note you make afterwards — adds to the run you are currently in. So the finish line you were shown at the start is the finish line you actually get.

The one thing that does keep you in the session is a card you rate again, which returns in the same run rather than tomorrow. That is deliberate, for the reason above: a card you just failed has not been learned.

Someone I had never spoken to put the reason better than I had: infinite queues are why people stop opening these apps. The session ending is not a feature for finishing more, it is a feature for coming back tomorrow.

A limit worth naming. Quat has a daily cards figure on the dashboard, and it is a goal you set, not a cap — it does not stop new cards entering your deck, and it does not truncate a session. If your queue is too big, the lever is capturing less for a while, not the goal number.