I am addicted to caffeine as well, I just can't help it. Really I only take two or three coffees a day, but if at a certain hour in the morning I still haven't had one, then I begin to have a headache - not something unberable, but annoying indeed. If I have a cofee, then it disappears in a quarter of an hour or so.
Having said this, caffeine doesn't really work much: with precise referring to programming, I once had to do some coding for work after a week end in which I had basically slept one third of what I usually (need to) sleep every single night. I was so tired that I was continuously falling asleep: I tried having the whole output of a moka for five persons, but that just didn't make me less tired and sleepy. So I resigned and tried to sleep on it, but then while still being just as tired (or even more) I couldn't sleep!