Thank you both for your explanation. It was very helpful. I think the only thing that was not answered had nothing really to do with powerpress or podcasting, but how the Apple IOS Music app handled Podcast Episodes in general, which basically they dump them all into one directory. So even if two separate feeds were used, but both linked to the same file, the end result would be the same. The client would only have that episode in one or the other Podcasts. Going back to what Mike had suggested:
With the desktop iTunes app, that's not true, it will rename the file based on the title of your blog post and if the file exists already, it adds something to the file to make it unique. Not sure how the "Podcast" app works on iOS though, but I don't believe the file is saved based on actual file name, but stored based on the feed item itself. We'll never know because iOS doesn't let us see the files in apps.
A series of episodes,some refer to this as a "season", you should be putting them all in the same podcast feed. You can use categories to offer a category of season 1, a category of season 2, etc... but the main podcast feed (category or not) submitted to iTunes should be your program regardless of season or series. This is default podcast behavior. But if you want to do this differently, you can, just keep in mind every podcast you submit to iTunes needs a new unique title, so you'll have to say "Podcast name 2013" for 2013, and next year submit a new feed Podcast Name 2014", or something like that. I wouldn't do that for a number of reasons, you're going to confuse folks, others are going to find your older season and not know there's a new season next year, etc... The idea of podcasting is to make it easy for folks to subscribe and stay subscribed. Making folks re-subscribe every year or series defeats the purpose.
Podcast Channels (not podcast categorizes) is what you want to syndicate other formats, like eBook, PDF, video, etc..