I used to drink coffee by the gallon. I once worked in an office full of caffeine addicts. We'd drain two of those big steel industrial coffeemakers a day between only 6 of us. The next morning we'd reheat whatever dregs were left at the bottom from the previous day rather than wait for a new batch.
That changed a few years later when I was on the road full time. Getting coffee usually meant getting up, getting dressed, and going out into the environment in a haze. One day I just said fark it and skipped the coffee. After a week of that, to my surprise I started waking up feeling as if I'd already had my coffee! No grumpiness, no slow reflexes, no more staring blankly at the ceiling for 10 minutes just thinking about getting out of bed.
For the next 20 years I pretty much swore off coffee. Between waking up alert and never having trouble falling asleep, it was like getting an extra hour a day.
Of course, I've since grown out of that phase. Nowadays I really enjoy the stuff, and just try not to overdo it.
Beepster: thanks for asking about my back. No muscle relaxers yet, or any other therapy. Doc won't prescribe anything until I've had an MRI, and that took over two weeks to schedule. Finally had it done yesterday. But I am healing: instead of 12 Percocets a day I now get by on 6-8 ibuprofens and a doobie.