Currently, we only have a 30 day plan and a 6 month plan. If you can't decide between the two, we would suggest purchasing the 6 month plan to give yourself the most amount of time to study, especially if you're not 100% sure about whether you may have to retake the test, or may have to push your test date further out into the future, based on your progress as you study. However, if you have the time and energy to study intensively for one month, the 30 day plan has the same score guarantee as the 6 month plan (improve your score by 5 points!).
We do this because we incur costs based on the sale and based on product usage, not based on time. So we wouldn't want to charge a student more just because they took more time to answer the same amount of questions as another student. Conversely, we also don't charge students less just because they answer questions faster :).