Heuristic
Promote mature vocabulary into maintenance
A mature word should earn distance.
When it fits
- A review queue keeps growing because mastered items never leave frequent rotation.
When to avoid it
- Low-frequency but mission-critical vocabulary may need maintenance even when it is currently strong because natural exposure is unlikely.
Why it matters
When an item survives delayed productive retrieval and still behaves correctly in a new context, lengthen its interval aggressively or remove it from frequent review. Use ordinary reading, listening and real production as additional contact. Reserve dense review time for fragile, high-value language rather than paying a daily tax on words that have already proved durable.
An example
A work phrase recalled accurately over several long intervals leaves the daily deck; a rare technical term remains on a slower maintenance schedule.
Check your result
Frequent review contains mostly items that still benefit from near-term retrieval.
Keep this limit in mind
- Low-frequency but mission-critical vocabulary may need maintenance even when it is currently strong because natural exposure is unlikely.
Evidence and sources
Spaced practice has a medium-to-large positive effect on second-language learning; longer spacing is more beneficial than shorter spacing on delayed tests, while equal and expanding schedules were statistically equivalent in the meta-analysis.
The evidence does not yield one fixed interval sequence that is optimal for every learner, item and retention horizon.
The Effects of Spaced Practice on Second Language Learning: A Meta-Analysis · Abstract
Intentional vocabulary activities can produce substantial immediate learning, but delayed recall is lower and outcomes vary widely by activity and study conditions.
Average gains do not tell an individual learner which specific words will remain usable in spontaneous production.
How Effective Are Intentional Vocabulary-Learning Activities? A Meta-Analysis · Abstract