How Long Is Too Long?

I would like some feedback from the audience about optimal lengths. We have a conversational broadcast where we need to fit three or four people's ideas into a a segment. So, i mean, it shakes out to about an hour o 15. I don't sit down and be like, this is what's going to entertain me for the next hour and a half. The material is kind of, we just go, hey, if we said, ever we want to say, ok, it's getting along anyway. And then i listen to david harvey's marxis lectures on capital. And they're about two and a half hours. But you know, my listening habits are different