" Extra repetition is known as overlearning, and it doesn’t help long-term memory at all. Can you remember a single fact from the last school test you crammed for? Can you even remember the test itself? If we’re going to invest our time in a language, we want to remember for months, years, or decades. If we can’t achieve this goal by working harder, then we’ll do it by working as little as possible. "

― Gabriel Wyner , Fluent Forever: How to Learn Any Language Fast and Never Forget It