After returning to work after the birth of my daughter, I take a large thermos to work that holds about a liter of coffee and it is usually empty by the time I get home. It's about 7 cups. Not healthy at all, but neither is sleeping for four hours a night.
Usually two ceramic coffee mugs full when i break out my French press. That or a 16 oz mocha. I rarely drink it after noon except in social situations.
One cup when I first wake up and one cup when I get to work during the week. During the weekend I might have a cup when I first get up,. but most of the time I don't drink coffee during the weekend.
About 40 oz a day. More if I have a headache--one of the many things caffeine will cure. If it's around, I'll drink it until about 30 minutes before I want to fall asleep.
On a normal weekday morning, I'll have 2 or 3 double-Americanos and sometimes, a double shot before walking out the door.
If I'm working from home or on a weekend, 6-8 doubles.
I try not to have any Espresso after 2:00 PM, as someone said above, so I can sleep.
Here's an interesting note for anyone out there watching their weight:
My father (a retired GP), tells me that caffeine has pretty strong effects on your ability to lose weight, in 2 ways:
Water intake - For every cup of coffee you have, you need to drink 2 more 8 oz glasses of water over and above your normal requirement of water intake.
Fat loss - He says that while the medical community doesn't really understand it fully, somehow the body recognizes an artificial stimulant and tends to hoard fat. So the more coffee you drink, the harder you have to work to lose the same quantity of fat.
It's recommended (by many programs, not just my father) that a good diet regime should include only 1 cup of decaf a day, 2 at the very max.
Most of a pot in the mornings less a cup or two the Mrs. may have, and occasionally a couple of cups in the evenings depending on if the mood for coffee strikes me.