I agree that the length of time doesn't really matter.
It is more important that how intensly you study.
I studied like 5 hours a week for 6 month (I know. I worked full time, and winter was really cold to sit on the chair and study)
Then for last 1 and half month, I studied really hard.
Right after the work, I studied from 8pm to 2am every day, and I studied all day on weekend.
I personally recommend to study intensely for short time.
That way, you are constantly in the mode of studying, and you don't forget what you studied.