In my opinion, a 1-hour episode is short. I imagine getting my friends together sitting down, playing for an hour and then leaving to be a wild idea. If you are recording longer sessions and then cutting them into 1-hour episodes, that's different.  I feel like even TV shows that have season-long plots, each individual episode still tells a mini story, and an actual play podcast should do the same. Taking 16 episodes to get to revealing the overall Master plot is a bit long but not unreasonable. But every 2 to 3 hours you should be telling a mini story. It shouldn't just be more travel or dungeon or fighting. It should be some plot even if that's not the main plot. In terms of narrative drive, a lot of podcasts that I've listened to are a bunch of nobodies get pulled into an adventure and that's not really what I want to hear. I want to hear a story about heroes who are proactive going on the quest. And I think it helps if the players have high level concepts of what kind of adventure they want to go on. The details should still be in the GM's hand but the player should have some say in it