Passed FE Environmental first try, 5 years out of school! (5 months prep)
I studied for about 5 months, fairly consistently (about 30-60 minutes per day). I used Mark Mattson videos first, and then did 1100 PrepFE problems over the course of those 5 months, getting to about 70-80% correct in all topics. For topics not covered by MM, I used a folder of FE Environmental study material put together by another very gracious (and organized) test taker that I found on this subreddit. It included video links to topics that are hard to find info on in typical Civil FE study guides (such as Air pollution, wastewater, solid waste), plus some practice problems. I created a Quizlet with common formulas and terms I needed to know, and skimmed through the entire FE Handbook to make sure I knew where everything was.
About 5 weeks before my exam, I took the online NCEES Environmental practice exam Vol 1 to see how I was doing. I got a 52%, but I had not studied 3-4 of the topics yet so I knew I could do better. I completed studying those topics (though I was very light on thermo review because it was only 3-5 questions), and 2 weeks before my exam, I took the Anthem books practice exam and scored an 80%.
A week before my exam, I took the paper NCEES Environmental practice exam. I only scored a 60% on this, so I was a little nervous going in to the real test, but I reviewed all my errors and saw that a lot of my mistakes were units/not reading the question fully but I had the concepts down.
I felt nervous going in to the exam, but I felt pretty good about the amount of studying I had put in (I think about 200 hours). I whipped through the first half in an hour and half and spent 20 minutes checking my answers before turning it in and taking my break. I didn't want to drag the first half out too long as I knew the second half would be harder, so I guessed on one or two questions to save time.
The second half was harder, but I was a little surprised that the test as a whole felt easier than all of the official NCEES practice exams I had taken. It was more on par with the Anthem books practice exam (which I felt was a bit easier). I finished the second half with over an hour to spare to check my answers, and I basically re-did every problem to check them. I found 3 unit errors so I'm glad I caught those. I did guess on maybe 4-5 questions on the second half too. But I walked out of the exam room feeling really confident.
This has been a lot of work but I am so glad it paid off and I'm setting my sights on a future PE! Good luck all who are studying.