At the other end of the scale are podcasts that are a few minutes long - daily briefings, the news, etc. I've always found these hard to listen to in normal podcast software since they're meant to be ephemeral and quick, so I've been working on a new approach: http://briefings.fm/
I agree on both counts. A 5-10 minute podcast often feels like it's "not worth" selecting and playing--at least as part of a standard podcast queueing and listening flow. At the same time, a straight interview/discussion without a lot of production work to break it into segments, etc. that's an hour feels too long. (And producing a radio show rather than just putting an interview up is a lot more work.) I find the interview podcasts that I do naturally gravitating into the 20-25 minute range.
There seems to be a market for all kinds of lengths. I like the 60-minuteish with some banter but mostly on topic. I mostly listen to podcasts while walking or doing the dishes or something like that so I'm not super focused and the longer and slower podcasts work best for that. Running the garbage disposal or a truck driving past won't force me to rewind. If they go to multiple hours I usually rather opt-in for an audiobook at that point.
Yeah, I'm totally with you on that. That's how I want my podcasts to stay. I do see the value in quickly grabbing an up to the hour briefing on something though, so want to explore ways to do that.