There are a lot of other videos from this same interview on YouTube; I plan to watch a bunch of 'em this weekend. Hat-tips to Mark Evanier, where I first saw the video, and Roger, who notified me of its existence via electronic pony express thing.
(Oh, and the bit of advice in question from Mr. Simon? I'm not sure if I follow that or not, to be honest. I tend to write until I'm tired and don't want to write anymore. On reflection I think I very well might follow this advice, but I've never really thought about it. I'll pay more attention next time I'm working on something new.)