I'd say about 1-3 months before. I did the month long class, and they say that you should take the test a week or two after the class finishes up, but I found that there was more study material available than I could finish that quick - there's LOTS of great stuff on the website! Also, Kaplan won't prepare you for everything, I don't know how I got an 18 PAT only using Kaplan, the actual test was so much harder.