It goes for just 15 minutes, and I'm trying to encourage them to leave it that short. Shorter podcasts can be listened to when you don't have time for an hour-long one. They can be archived more easily. You can fit them on a device with less free space (I'm soon upgrading my 1GB SD Card to a 2GB largely because of podcasts). And you can find stuff in them more easily. Suppose I hear a 5-minute discussion about something in an hour-long podcast that I like and want to re-listen to later. I have to keep the whole thing! As well as that, I need to remember whereabouts in the podcast it was, or else listen to the whole thing again. A 15-minute one still has the same problem, but those issues become less with a smaller file.
Those people who have known me for a while might know that for over a year I had a podcast about the Arsenal football club. I just recorded it on my PDA, typically in the car on my short commute. Occasionally I would abuse the traffic, but I don't think people cared. But because my commute is quite short, it kept the podcasts short too. I never had trouble with finding content, because there were always more games to discuss, or injuries, transfer rumours, etc. Tech-podcasts can be harder that way, but I think there is always enough content out there to have a 15 minute discussion with a friend which you record and push out there.
Podcasting: It's the blog you can read while driving.