I also started studying for the 5/31 MCAT in January. I was at the tail end of my research-based master's program at the time and was in the lab 40-60 hrs/week. Between January and May I probably averaged 2-3 hours of studying a day, but there were some days I didn't study at all and then I would study 5-6 hrs on Saturdays and Sundays. I finished my master's experiments in April and started a full-time research tech job, in which I also work 40-60 hrs/wk, plus I also went back to volunteering 5 hrs on Saturdays. Even though I wasn't studying 6 hours every day, I definitely was burned out by May. I didn't study bio much since I've taken alot of grad bio classes and taught grad anatomy and physiology, so I guess that saved me some study time. I spent alot of time on physics and organic chem, and a good amount of time on verbal (probably should have spent more time on verbal). I won't know until a week from today what my score is, but I felt decent about the sciences, but lousy about the verbal, so we'll see. Overall, I think 6 hrs/day is overkill if you're studying over several months.