I'm only a few exams in, but so far I've just been reviewing all my cards as they come due, even stuff from the previous exams. That, for me anyway, was kind of the point of anki - long term retention. You can, however, delete/suspend cards with any random details that you might have literally just needed for the test (but if you're doing it right, there shouldn't be too many of those types of cards).
The beauty of anki is that, over time, reviews for an old deck or whatever get shorter and shorter as they get more spaced out - it doesn't just cumulatively build up. That would be crazy.