1. You are assuming length ONLY by audio. There is no way to know how long the learner actually spends reading/exploring (assuming that you built in the option for the learner to explore **eyebrows raised**);
2. Every topic isn’t the same and therefore can’t be treated the same;
3. Every learner isn’t the same and therefore can’t be treated the same (different pace);
4. What if someone already knows a great deal about the topic? (different schema, background knowledge);
There are a few other reasons I can think of for not locking into specific lengths and numbers. Some objectives might be combined into a larger objective. Some thoughts can be clarified more easily than others. Some activities may cover more than just one objective. There are a lot of variables.
Since learners are individuals, each course must be treated as such. I am not suggesting that we create different courses for every person on the planet. But you really need to analyze the content for what it is and then determine how to purpose it for the learner rather than shoving the content into a pre-fab box and hoping that it fits. The square peg and round hole theory comes to mind. Of course there are principles that we should keep in mind. But with regard to some of these specific rules, I say, ditch ‘em. Who made them up anyway?
What are your thoughts?



Good note, Paul. I definitely agree that the prowess of the narrator and other pieces of the lesson play a part in how it is received by the learner. I have heard and seen some moss that are nor bad content wise but the audio was horribly distracting. That definitely affected my experience.
The rules get created through the application of several pressures. It may be the aggregate feedback of students that makes the rules. It may be traditionalism. It may stem from an egalitarian impulse to provide advice to others.
I agree though. Rigid containers chip easily once you try to use them. I think the rules you cite above come from a more recent set of best elearning practices, specifically around proper chunking. But the problem is still there, and you are right to point out that no two learners or concepts are the same. Further, the way each learner processes is different to a person as well. This is why properly chunked, fully-featured pieces is the best course of action. Some may read, some may listen, some may read, then listen or vice versa. And within that some may read fully and completely, and others skim for key words and selections.
I think there is room for consideration here, though, to consider the prowess of the communicators of the content (be they the narrators or the presenters). I think this counfounding variable can allow for differences in how effectively and how long a particular topic can be delivered. This is not to say that a great communicator that inappropriately watters content down is then better than a bad communicator that drones on but at the right detail level, but there are different ways to approach the same amterial.