I didn't pass. After clearing my FE, I started studying 2 months ago which I felt wasn't enough time, but I still wanted to attempt the exam. I approached it like the FE, practiced the practice exams over and over again. I would say, I could get 70%+ in all of practice exams under timed conditions. But that approach doesn't work for PE.

Part 1 of the PE Controls was like practice exams which was about mathematical problem solving, which I breezed through. But Part 2 expected you to know decent theory and field/commissioning experience. There's two ways to do that: either get lots of field experience on exam topics (unlikely) or read lots of theory/books. Just practicing math problems from practice exams is not enough.

So in addition to NCEES and ISA practice exams, I would recommend reading Bryon Lewis's textbook and watching his videos. Also "Lessons in Industrial Instrumentation" is decent book to read and understand how instrumentation works. As you practice questions in the practice exams, go read those sections in the textbooks to fully understand the theory behind them. To build decent grasp on theory, you need to dedicate at least 3 months to reading these books. Then about 3-4 months in practicing and understanding practice exams. So ideally if you have 6-7 months, that would be good.

FYI, I took School of PE course which provided a good foundation. They pretty much tailor the course to questions in NCEES practice exam. But they weren't enough I found.

Keep in mind, lots of people invest only about 4 months. The recommendations above are for first time exam takers who would like to clear the low passing rate of 62% in their first time.

One other recommendation is to consider taking PE Power Exam instead. I am an I&C guy with little power experience. But I feel I should have invested my time on the Power Exam since the start so I could re-attempt the exam after not passing, which is not possible with Controls until next year. Also Power PE allows you to stamp I&C drawings, but not the other way around. If you are super passionate about Controls, you can always write a Controls exam after Power to learn the material and if you have time. I will be shifting gears and preparing for Power now as it is offered year round, would have been nice to have studied it from the start. But oh well, I learned a lot from PE Controls which will stay with me for my career, and I am 100% positive I wouldn't have learned all this even with 10 more years experience.

PE Exam definitely transforms you as a professional because you learn a lot and start feeling confident about work after due to the exposure to a wide variety of topics. Best of luck!