In the past, some teachers recommended a way to systematically review vocabulary based on a schedule where the time intervals of review would become longer and longer. I tried to figure out what that would be like for the student.
If a student 'learned' 20 words on Day 1, reviewed them the next day, then 3 days after that, 1 week after that, 2 weeks after that, 1 month after that, 2 months after that, then here is how many words the student would have to review daily.
20, Day 1
40, Days 2-4
60, Days 5-11
80, Days 12-26
100, Days 27-56
120, Days 57-116
140, Days 117-unlimited
We assume the student starts his project on Day 1 and everyday adds 20 words. If my calculations are correct, if the student stopped reviewing a word because he knew it on Day 118 (after about 4 months), then his vocabulary review load would level off at 140 words a day.
By the time he is supposed to know the word (after 117 days) he will have reviewed the word 7 times.
He will be learning new words at a rate of about 600 a month which would be more than 6000 per year.
We have to acknowledge that this would be only a passive understanding of the word, perhaps useful for reading/listening. But it could provide an 'introduction' to the word that through further contact with the word in extensive English input could turn into an active understanding of the word useful in writing/speaking.
I think such a thing would be doable but only by highly dedicated well-organized students. For most students it would probably be too challenging. Perhaps if the student limited himself to 10 or even 5 words a day it would be easier and he'd only have to review 70 or 35 words a day.
Would reviewing the word 7 times be enough to hold onto it and allow extensive exposure to kick in and help the student keep the word I don't know.