To learn a language as quickly as it often depends on the language. If you do not have a review for you to forget what you learned when previous and want to start again, which is a waste of time.
The study results were based on the use of language often if you do not have a review for you to forget what you learned at other times, and then have to start again. This is a waste of time
Language learning results depends on the use of language frequently, if you do not review any longer. You forget what you learned last time, and have to start again. Which is a waste of time.