You should be able to do it in 30 days.
I went through the tapes in a week, with about a tape or two a day, some days none.
Like Andy said, don't put constraints on yourself. Relax, and don't make it seem like a chore, or something you've got to do.
I learned it quite quickly and am still improving. But the improvements were so great everyday that I was always amazed and still am.
