I am an engineering student myself. I do electrical power engineering and environmental engineering, plus some applied physics and numerical mathematics at a Uni in Norway.
My record for staying up in one long stint was 60 hours, knocking out three different project reports. My brain thought it sucked so bad it nearly refused to come back online after the 20 hours of sleep I needed afterwards. My advice is: fuck it! Study however you need to. It might be a good idea to force yourself to concentrate even when you do not feel like it, but if you really are tired and need sleep, it is because you really are tired and need sleep :-) Our brains are funny that way; telling us exactly what it needs, if we just learn to listen.
In general though, it helps to take breaks, and to keep hydrated and that kind of thing. Also, working out helps a lot on concentration; for me anyways.
I hope you figure this out, and you'll kick ass on the exams! :-D
Ghini
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