The results from our analyses suggest that concentrating the hours of English instruction in shorter periods of time is more beneficial for the students’ learning than distributing them in many months.

Contextual interference, for instance, tends to be helpful, but it can backfire for complex skills or poorer students. Similarly, retrieval practice tends to be helpful—unless the person can’t retrieve what they’re trying to remember.

Serrano and Muñoz cite one study that evaluated qualitative performance from intensive/extensive studying schedules and found the intensive classrooms had better group cohesion and motivation.

A well-known consequence of the spacing effect is that massed presentations tend to be more effective initially, but their advantage typically fades over time.

Intensive projects should be followed by more leisurely maintenance. Even if an intensive burst can get you quickly to proficiency, it probably makes sense to continue to practice at a more leisurely pace for months or years after if you don’t want that proficiency to decline too abruptly.