I agree with mathwonk here.
It sounds crazy, but that's the reality to doing well. I haven't done all of that, but I wouldn't be surprised if I did in Graduate School.
The whole purpose of writing your own exams is to force you to stop using the information at hand. This forces you think, and solve without help. In the end, if you get anything wrong, you now know your limit to the information you know. Therefore, study that for a bit, then write another practice exam and see where you can't get through.
If you already solve problems without looking at the information at hand, then it's all good. I think you're totally fine here because you aren't being dependent on the information at hand. The only problem now is basically how fast you solve the problem. Basically, I just ask myself realistically, am I fast or not? If not, then work FASTER! If you don't know, write a practice exam and find out if you're fast.
The only problem that comes from writing practice exams for me is that once I write/read the question I probably already know how to solve it and/or a method to do it. Plus, I'll remember the question 100%. I'd still remember it if I wrote it a month ago! Another problem is that if the solution does not pop into my head, I'll ponder about it until I got it because I love the challenge. Of course, I can always put hard questions on, but then that goes beyond the difficulty of the midterm, which is fine, but I like to do these on my own time rather than for study time.
Anyways, my philosophy to doing well in classes is to focus more on the understanding and learning of the material. It's not so easy these days because the focus is shifting into learning-how-to-pass-the-midterm rather than learning the material itself. As well as professors are teaching-you-to-pass-the-midterm rather than teaching the material itself. I don't blame anyone for this because that's just the result of having so many people in university focused on getting the degree for the job and not for the learning or actual education.
Like, for example, I suck in probability. But in reality, I'm probably one of the better students in the class. I say I suck because my understanding of it is weak. I can solve problem after problem, but give me one problem that is vastly different (but same material) and I'm probably screwed. Of course, I'm probably ready for the midterm and can do well, this isn't my goal. Why? Because if I understand it, I'll probably never forget it for awhile and that's what counts. (Even though I hate probability, the remembering part is beneficial because when I study for finals, I'm half way done.)
I met students with higher marks than me in Linear Algebra, but yet in a third year class a linear transformation question came up and I was the only one able to understand it or even answer it. As a TA, I feel fairly comfortable that you can ask me anything with regarding to the text because I did it, I understood it, I remember it, I studied it, etc...
I met students with higher marks than me in Calculus, but yet I understand it more than them. Some forgot Green's Theorem!
The more I understand it, the less I need to study. And so, that's my method.