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Meandering down this diversion a bit... First, yes, I generally agree with you. What I've noticed listening to a lot of lectures over the past few years are typically breaks at roughly: 90s, 5m, 10m, that 20--30m spot, 45--60m, 90m, and very occasionally a longer session, though I'd argue that 2h is about the maximum which can be sustained in a single session. The shortest are just teasers, often commercial broadcast. They're not informative but more advisory , and really only advertisements for some additional content, which is the medium's strength.[1] A 4--10m segment is a brief introduction to a topic, beginning with about the span of a noncommercial broadcast, and including the typical length of a quick YouTube video. You can actually cover quite a bit of the basics of a topic, or mesh together a number of topics into once related thread. At 20m you're hitting one of the natural spans of human focus and the point at which attention starts to wander without some form of internal break or diversion. Longer presentations are often a fusion of 2--3 15--20 minute segments. I note that many well-structured podcasts aim for about this mark ("History of Philosophy" by Peter Adamson comes to mind.) If you're aiming to fill a 30 minute timeslot, 20--25m allows a bit of additional padding on either side for other filler as well. Lecture presentations tend to run variously about 20, 30, 45, 50, or a full 60 minutes. Typically there's a Q&A session, and in an academic context, an int