When you are recording, you will inevitably fumble words or phrases, and miss key emphasis, so you will add a lot of time doing retakes. All that time spent narrating can make you physically, mentally, and emotionally exhausted. When exhaustion sets in, the Narrator's voice slowly walks out of the building.

If you let your concentration flag, even for a moment, your own voice takes over. But when that happens, you are doing little more than reading your book out loud. You may not be aware of it, but your listener will be instantly aware of it.

What does the listener hear when this happens? A voice that has lost its spark, its edge. A story that no longer holds the listener's imagination.

It is too easy to say to yourself, “I'll just do a couple more pages,” when your energy level is dropping like a brick. Recognizing exhaustion is one of the best reasons for getting someone else to work with you when you are doing the recording. Your friend will hear changes in the presentation that you don't hear. Your friend can tell when you need to stop and take a break.

If you are going to record alone, then you have to discipline yourself to stop earlier rather than later, and take reasonable breaks in between recording. If it feels like you are pushing it, you are pushing it.