Language proficiency tests, professional certification exams, entrance exams. Studying toward a fixed exam date differs from open-ended study in one decisive way: you know exactly how long you need to remember the material.
That is actually the best possible condition for planning reviews, because research indicates that the optimal review interval depends on how long you want to retain the material.
The optimal interval depends on the distance to your target date
In 2008, a research team led by Cepeda ran a large-scale experiment with 1,350 participants, combining different review timings with different lengths of time until a final test. The conclusion was simple.
- If the final test is close, use shorter review intervals
- If the final test is far away, use longer review intervals
As a rough guide, the optimal review interval was reported to tend to fall at around 10–20% of the time remaining until the test. For an exam a month away, that means reviewing every few days; for an exam six months away, every few weeks. (The precise optimum varies with the material and the individual, so treat this as an order of magnitude.)
There is no single "correct" review interval. It is only determined by working backward from your exam date.
In other words, the review interval is not a universal constant. It is determined only by working backward from your deadline, the exam date.
How to build a backward plan
Turned into concrete steps, it looks like this.
- Fix the exam date. Every part of the plan is worked out backward from here
- Separate the period for learning new material from the period focused on review. If you cram new material right before the exam, you will not get through your reviews and both end up half-done. As a guide, shift the weight toward review for the final 20–30% of your study period
- Starting from the day you learn something, schedule reviews at widening intervals. Spread them out: the next day, then a few days later, then one to two weeks later (for the evidence, see the article on spaced repetition)
- Place the last review right before the exam. Even well-established memories fade over time, so a final check a few days before or the day before the exam makes your results more reliable
Planning with this structure guards against the most common failure in exam preparation: "I covered the whole syllabus once, but by exam day I had forgotten what I studied at the start." It works because material from the early part of your study accumulates the most reviews.
Last-minute review is not "bad"
Explanations of spaced practice tend to cast cramming as the villain, but to be precise, the problem is cramming alone. Focused review just before the exam is valuable in itself.
- Build the foundation with spaced reviews (this is what carries long-term retention)
- Polish the surface with a full review right before the exam (this speeds up recall on exam day)
This two-layer approach is the strongest form of exam preparation. Cramming at the last minute without a foundation, on the other hand, fades rapidly after the exam. That is what is really behind "I passed the exam but nothing stuck." The more you will use a qualification in your actual work, the more it is worth investing in the foundation.
When you have multiple subjects or study materials
In real exam preparation, several sets of materials run in parallel. Two things keep the plan from falling apart.
- Stagger your start dates. If you start every set of materials on the same day, their review dates also land on the same days and arrive in waves. Simply starting each a few days apart evens out your daily review load
- Estimate your daily review load first. Reviews generate "today's share" every single day. Adjust your pace of new learning so that the load stays manageable
The heart of the plan is getting to a state where, every morning, you know without hesitation what you are reviewing that day. Once that part is systematized, the rest is just steady repetition.
Summary
- The optimal review interval depends on the time remaining until your exam (shorter if it is close, longer if it is far away)
- Plan backward from the exam date. Shift the weight toward review near the end, and place the last review right before the exam
- A full review right before the exam works well on top of a foundation built with spaced repetition. Only cramming without a foundation is a trap
- With multiple sets of materials, stagger the start dates and adjust your pace of new learning so the daily review load stays steady