I would say that don't go on the numbers presented here. It's different for every individual.
Greater study hours doesn't guarantee you will pass. It's how much smart study you have done. If there was a number of study hours required to pass then we won't see this many examinees being unsuccessful.
The hours that really count are the hours that you spent preparing yourself "according to the test". I took School of PE course (70 hours) and invested another 30 hours (max.) or so for my preparation. This includes collecting the references and organizing everything. Of course, my aquaintance with AASHTO, MUTCD and other references helped me as I have been using them regularly at work. But I would say that the prep course was VERY VERY helpful and I recommend the prep course (Testmasters of S of PE) to all who can afford to spend that much time and money. It was a good investment now when i look back. The course alone won't get you to pass, but it will teach you a lot and basically consolidate your study material.. Plus, unintentianally I was prepared to sit for long hours on a chair and table environment while working problems in the prep class.. this helped me counter stress and fatigue during the test. i would say that during the test, physically and mentally i wasn't tired as much as i had expected or i was during my FE test..
I passed CE/Transp. first attempt - October 07. I had CERM and prep course binders (I had split the huge binder in to 3) on my table all the time.
Hope that helps.
-V.