unplug, caffeine has a half life of 10 hours so you should drink it at the beginning of your shift. I work overnights by myself, too, and the only time I consume coffee is in the first 2-3 hours because it's kept me awake before. I also use medication to sleep, though, because I'm wide awake half of the time when I get off.

It's true, though, sometimes I bother people all night to talk to me on facebook until 1-2 in the morning to curve the loneliness of working alone.

I drink 1 1/2- 2 cups when I do drink coffee. I don't recommend it for teenagers though because its habit forming.