I recently had an assignment to photograph 54 portraits in under an hour. I have shot similar assignments for this client before, so I knew pretty much how the schedule needed to go. The company needed both individual and group images of 54 people for an upcoming piece of literature that they're producing in house. The images are all going to appear close to each other, and therefore consistency is key. I set up a medium sized soft box against a wall in a small conference room. I marked a spot on the floor where everyone should stand, and was able to shoot everyone quickly without too much fuss.
The image below shows all 54 headshots, plus my test image. The total time to shoot the individual and group shots was just over 40 minutes.