Once a student came to me and was adamant that we only focus on math until she had finished going through all the vocabulary words. For the first month of our sessions, I acquiesced.
About six weeks into our meetings, I surprised her one day by asking her for the definitions to common GRE words. She didn't seem to know the definition to any of the words, though she assured me she studied most of them at one point.
Did she mean she learnt them in high school or in college? When I asked, she told me they were at the beginning of the vocab list she was going through.
But now she was around the 3,000-word mark (with 500 more to go) and couldn't seem to remember any words from more than a few weeks ago.
Luckily, I dissuaded her from wasting any more time going through the list sequentially by asking her the simple question: how many words will you have stored in long-term memory after you have reached the 3,500 word mark?
It's about long term memory
To push your GRE scores through the ceiling you have to commit words to long-term memory. And to commit words to long-term memory, you have to become a master of repetition.
Revisiting words from weeks before is helpful, especially ones that you struggled with. I should also add is that you should get rid of the list altogether, or at least turn the words you see on a list into flashcards (this is easy to do via Quizlet).
How do flashcards measure up?
With flashcards, you can constantly return to previous words, separating words that you've mastered (though eventually you'll want to come back to these) from words you struggle with.
Yet, even flashcards are not enough. You'll want to go beyond mere repetition and try to create as many learning contexts as possible. By learning contexts, I mean associations you have with the word.
This can be anything from the physical location of where you learn the word (on the couch, on public transportation, on the wall where you've written down the word on an index card) to the associations you have with a word.
For instance, I'm a lot more likely to remember a word when I look it up on vocabulary.com. This site not only gives you a creative description of the word and a colorful example, but there are example sentences drawn from across the web.
What else can you do?
Also, use a word whenever you can. Hurl invectives such as truculent, pugnacious, and bellicose at the person who cut you off on the drive to work (you may want to do so with the windows up).
Or on a positive note, you can describe how you are sanguine about all these auspicious signs in your life. The bottom line: use it or lose it.
Finally, there is plenty of online GRE practice in the form of Text Completions and Sentence Equivalence questions. Words you've been studying will pop up, reinforcing the association you have with those words. And words you don't know can be added to your flashcard collection.
As for my former student, she ended up committing thousands of words to long-term memory once she ditched the word list and adopted the strategies above.