It depends how much time you can devote on the daily basis with your job? For part 1 - i spent close to 5-6 months for studies with almost 30-45 minutes of study on the week day and around 2-3 hours on weekends.
For part2 and part 3 -it took around 150 hours spanning around 2.5 months.
I will suggest, SCEA5 requires momentum-you don't have to break the continuity in all the parts. Try to do all the parts without any gaps.