3 weeks is enough time if you spend it wisely. I'm using Roger, and I passed BEC on 8/29/15. I started studying on 8/1, but I didn't do so consistently until around the 10th. I took some shortcuts because I scored a 74 on BEC in 2014 without any studying at all. I have a lot of background knowledge because I am interested in inflation, etc. and like to read about the economy. Here's how I attacked it:
Week 1: I wanted to make sure I focused my time on my weaknesses, so I made pretests from Roger's test bank. For each section, I took a 30 question quiz and if I scored 70% or higher, I skipped that sections's lectures entirely. My reasoning was I could pick up additional points by drilling more MCQ's. I wound up skipping 50-60% of Roger's lectures for BEC by doing this.
Week 2/Part of Week 3: Watched the lectures for the sections I needed to, and took more quizzes after each section to make sure I learned the material. Periodically, I included a WC in the quizzes to make sure I understood how to do them.
Week 3: For my review, I did all of the MCQ's in the book and made sure I read the explanations to the answers to understand why I got the question right or wrong. Call me old-fashioned, but I like doing book questions to review because it forces me to slow down and absorb the material before I move on. During this time, I also took the NASBA practice exam. It's helpful to do this to make sure you know the software that will be used on test day.
About the WC: Don't spend too much time on WC – in studying or while taking the actual exam. Roger does a really good job of breaking down how to do the WC – you get so many points just by repeating either what the question is asking, or summarizing your response in the conclusion. I think WC are only worth 15-20% of the exam. They are important, but not nearly as important as the MCQ.
BEC - 88 8/29/15
REG - 82 11/14/15
AUD - 83 1/8/16
FAR - 80 2/29/16