Speaking about Audio

In this week's class, we discussed the effectiveness of using audio narration with images rather than using images and printed text. This is supposed to help prevent cognitive overload where too much information is being processed through the visual/pictoral channel. We did not go in great depth about it, but I wonder if this suggested rule applies more to e-Learning courses that do not often change. I work in a retail environment and our content is constantly being updated. Sometimes we've gotten audio recorded and the project is ready to roll out the door, and the entire concept changes mid-stream. This involves re-recording and re-coding, since typically you should include a close-captioning option. The majority of our online courses do not have audio, but some of our courses that are created in Adobe Presenter do have audio attached because it's so easy to include it.

Is there a happy medium? Or is it something that designers and clients determine on a case-by-case basis?