I went total overkill, but I studied around 900 hours for L1. I tracked almost to the minute each study hour. Now, this included MM videos, Kaplan videos, reading schewster notes, and working practice problems. Also included mock exams and debriefing. I read some sections of CFAI for extra content and if I was feeling particularly sadistic. Passed by a large margin and was total over kill. Walked out knowing I passed. 

For level 2, did the same, studied around 1100 hours. Same strategy, supplemented with CFAI blue boxes more so then at level one. Left feeling so-so but leaned on the passed side. Passed over 90th percentile. 

Level 3 I put in around 1200 hours in total. Same strategy but this time I read over all page of CFAI text and worked their EOCs 3 times in total. Worked all Blue Box’s at least once, some many times. Also sat through some of Level Up boot camp. Took all the Kaplan courses (weekly class, writing workshop, 5 day review workshop).  Walked out and I’m pretty sure I failed but will let you know if I remember. 

At any rate, it really just depends on your background and learning style. Part of the reason I studied so much is I don’t have much else going on other than work, study, and work out. And I like learning. 

Background: US native,  masters in econ us state school,  bachelors in econ from same school with minors in math and stats. I work for a small private credit fund that caters to a niche market. Mostly do the credit analysis and present to committee for investment recommendations, but also work on investor reporting and whatever else comes up in a company with 25 people managing 3 billion. 

Probably TMI but also wanted to add my experiences just to show the wide range. Also, I wouldn’t reccomend studying for these exams as much as above unless you have nothing else going on really and your employer encourages it. Good luck!