We did a production of "The Misanthrope" in which there were 20 light cues for the entire show (and some night, there were more light cues than people in the audience). It was tough to keep anyone awake during that show, but I gave folks little toys to play with, like the gifts you get at kids parties (pin ball, get the ball in a hole, hang man, that sort of thing). We also chat on the headset - not the thing to do when you've got a cue heavy show, but it does help pass the time during long periods. Mostly I just keep telling myself that this is my job. I get up and move around a little, study the audience, whatever it takes. I have, on occasion, drank large amounts of beverage just so I would be uncomfortable enough to not have to worry about falling asleep. Not a great way to do it, but necessary during some of the Revivial stuff.
Charlie