Here's a possibly-fictional quote by Bruce Timm:
Allow me to explain, lest you judge me a traitor and stop reading. In your opinion, which would be better: for the DCAU to end its run at the top of its' game, or peter out in mediocrity a few seasons from now? Think about it—the critical acclaim about how good Unlimited is rivals the acclaim that the original Batman: the Animated Series received. Wizard Magazine recently declared that Unlimited was the best animated show on the air, and it seems you can't swing an Nth metal mace without hitting an article that just gushes with praise for the show.
Let me jump in and say "peter out in mediocrity."
Some of the best episodes of acclaimed shows came during their downward slide. There's still good work to be done with this series, and Cartoon Network is cancelling all the best reasons I have for watching their channel.
Really, at what point does someone say "We're doing great! Let's quit!"
Update: I'm still looking for recommendations for first novels published in 2005-6.