Dammit, how many times do I need to tell you? Efficient work is better than hard work. 50 exams isn't going to help much more than say, 10 exams. If you plotted the graph of "number of exam papers completed" vs. "study score" it would asymptotically approach 50. Your biggest gains would be your first few papers.
I'm saying this now because I don't want you to ever look back and say, "shit, I didn't make my goal: now I can't be confident about doing the actual exam!" That is wrong, you can be confident having only done as little as 5 exam papers. Just keep up consistent study habits: this is so much more valuable than high-volume cramming.
I'm sorry coblin but I think that is wrong.
For all my subjects that allowed it (chem, physics, methods, further), I did as many exams as I could. I didn't 'cram' as you suggest, but rather did 1 or 2 (3 or 4 for further generally) each day for a fair while. Doing practice exams is the best way to help, and I don't think that saying that doing 50+ is useless is good advice at all.
If a student is able to do 50+ without cramming and spreading it out and all that, then they should, because they are the best thing for studying. I did none of them in full exam time, and often I'd leave a question or just do it very quickly, even checking the answers as I went. Nonetheless, I did atleast 25 for physics, 30 for chem, 50 for further and 30 for methods, and I think I got pretty good scores for them.
Just for clarification, further exams generally took 20/25 mins, physics/chem 45 at max and methods around 35 mins for the 1 hour, and 1 hour for the 2 hours.