[Roxo]

That depends on what knowledge you're trying to retain. When I majored in Spanish in college I was extremely efficient compared to my classmates. Whereas most would memorize lists of words and sentences and dedicate tens of hours to it, I would average less than 5 hours of preparation time per exam.

[redmaverick]

>> When I majored in Spanish in college I was extremely efficient compared to my classmates.

Did you use spaced rep?

[Roxo]

Yes. After class, I would review my notes and add new items. Reviewing for exams amounted to those 5 hours average, spread over 3-4 weeks.