Did it with French, got an A. I revised for about two hours the night before my writing exam. Did no revision for speaking, listening or reading either.
Languages are different, though - if you're good at them and naturally retain vocabulary and grammar and the like, it's okay. With subjects that require more memorising or understanding how it works, I certainly wouldn't recommend it. (I was ill during my exams and that was probably the only revision I did at all.)