Good question! That really all depends on how involved the shoot is. Often times we need to rearrange the area where the shoot takes place to make room for all the gear and ensure the shots look great through the camera lens. Lighting is also a consideration and takes some time to get right.
Another consideration is the performance of the on-camera talent. Some people are naturally comfortable in front of the camera and need only a couple takes to nail their lines. Other people, not so much! If this is a concern, you may want to consider the addition of a teleprompter to the shoot. Teleprompters give an added boost of confidence to the speaker, help with remembering the script, and can really speed the shoot along.