Ideal Podcast Duration

Some of you may have noticed a poll on the left side bar on our home page.  These polls provide a great way for me to aggregate your feedback on how to improve the podcast.  When I first started this podcast my target duration was 15 miuntes to a half hour.  Then I started interviewing all these interesting people and my duration shot up to about 45 miuntes.  I actually edit the hour long interview down quite a bit, but they are still longer then I planned.  Maybe that is a good thing.  Let me know what you think.  How long would the ideal podcast be for you?