I'm sure this has been discussed before, but I wasn't sure how to phrase the search (or the subject of this post). When I haven't been able to study for a while, and come back to say several hundred/thousand reviews, I feel like I don't see any of the words I get wrong until I've worked through the entire thousand reviews at least. If I mark them as "not-sure" after several weeks of not studying, then I won't see them for another few weeks. Maybe I'm just being paranoid that I'll forget them before then, but is general best practice better to mark any that you are unsure of in a long queue as just "wrong" so hopefully you'll see it again sooner to reinforce what you've forgotten after a break?