After college, I gave up coffee for a few months because I was drinking up to 6, sometimes 8 cups a day. I got into a habit of making a cup in the morning, getting one with lunch, and having another mid-afternoon. Occasionally I would have another one or two in the evening. I though I was drinking around 3 cups a day until a good college friend made a comment about how much coffee I drink. I told her three cups isn't that bad and she looked at me like I was crazy. She gave me the wake up call that I'm not drinking three cups because my coffee mug holds two cups, so it was three "cups," but really six servings.
Luckily I did not go through withdrawals or get any headaches, but I'm very cautious about drinking coffee because I don't want to get back into a routine. I don't even make a cup in the morning because one cup occasionally will turn into a daily cup of coffee in the morning and slowly build up throughout the day.
I am not a coffee drinker myself, but I heard that apples are more effective than coffee in waking you up in the morning. I don't know if that is why you drink it, but I think it's an interesting fact.