"Are you surprised?"
I'm sorry you weren't as happy with the podcast with Kenny as you have been with some of the others; especially since you were so excited about that one. But I'm sure you handled it well. And as you say, you've just been doing this a short time so you're still learning things.

Jeeper's idea of asking, before you begin, how much time they prefer sounds like a good one. Or maybe you could ask when you're first arranging to do the podcast. That way you'd know in advance how to structure the format and questions.

At any rate, I'm enjoying the podcasts and I'm still looking forward to the one with Kenny.