Hiyaaaa,
Yes I agree with Turbulentmonkey but was going to say two weeks. I think I did all the work for Human Factors in two nights, but Nav for example is more substantial and you need to do lots of excercises to get workings into your head. Met I found alot of looking at the weather helped, on screen and looking up into the sky.
I really like this view:
Met Office: Surface pressure forecast
I must say I really enjoyed learning Met and Nav.
Cheers
Matt