I did my distance learning course with Cabair over 12 months with the exams divided into four blocks. I attended a week of groundschool two weeks prior to each set of exams followed by a clear week for further revision followed by the exam week.
I spent approximately 2 hours per day studying and worked full-time. Personally, I would have struggled to do the exams in 2 sittings and Cabair was the only school I found that scheduled them in 4.
You do need to be very disciplined to do the writtens via distance learning. It will take over your life and you will almost certainly become pretty tedious company for those around you who aren't really interested in the workings of a jet engine, global weather patterns, air law, schoolboy maths etc.
My best advice is try and enjoy it, learn and understand the subjects rather than memorizing assumed question banks by rote, set yourself up a quiet study area at home and stick to a realistic schedule - there is too much sheer volume of information to get away with last-minute cramming.