It really depends on the workload/how stressed I am. If there's not much work or if my mind is at ease, then I don't drink caffeine at all. However, if there's a crapton of work or my nerves are rattled, I chug coffee can after coffee can like there's no tomorrow.
I remember when I had my finals, I'd drink reallly strong black coffee with a lot of sugar to keep myself awake and concentrated during cram sessions. It's a wonder I didn't get diabetes or something, seriously.