You could make different courses for different weeks. So everytime a new week starts, you create a new course to import stuff into. This way you have the course for the current week as well as a course with the lessons imported last week, the week before and so on. Once you see no need to review lessons of a particular week, you can just delete the whole course.
Of course you don’t have to do this on a per week base. You could choose a different amount of days or just start a new course every X lessons imported.
You could simply add these lessons to a playlist that you create for this, and when you no longer want to review them, remove them from that playlist. You can even make multiple playlists for grouping different sets of lessons.
Otherwise, I like the idea of a “remind me about this lesson” function. We’ll put that in our wish list.