My entire GCSE History grade was based on cramming and last minute things-
We had 6-weeks to plan our South Africa coursework and gather our sources, etc. I did nothing for the 6-weeks, then on the night before writing my coursework essay, I found sources: I got 49/50 (lost 1 mark because of some spelling mistakes). Some of my classmates spent weeks of planning and drafting their coursework, and they ended up with marks like 30/50...
Then for my 2 exams, did no revision (too busy TRYING to revise AS maths) until the night before and the morning of both exams and ended up getting an A for both.
I wish I had revised more though, I could've gotten an A*
Plus, I suppose it didn't help the fact that I finished my first History paper with 25 minutes to spare, so I took a light, but much deserved, nap.