This NYT piece talks to Simpsons creator Matt Groening, who insists his show has found a second wind.

An excerpt:

even though some of its most ferocious fans suggest that it ran out of gas some time ago, the show remains in high gear, with 20 writers working on next year's season, searching for yet another joke that has yet to be told on "The Simpsons." An animated sitcom that seemed to lose some of its bite as it grew long in the tooth has been back in the news, with an episode on gay marriage earlier this year and later this season, a satirical, some would say sacrilegious, episode about the Simpsons' dalliance with Catholicism and another about the apocalypse. "The Simpsons," which had become as familiar as a pair of Homer's roomy trousers, has found a way to get its finger back in the eyes of viewers.

Mr. Groening, in spite of his own hints in previous interviews that the show might be running its course, has found a second wind. "I think the show has almost reached its halfway point, which means another 17 years," he said - and this of a show that is already the longest running now on television.

James L. Brooks, the veteran television producer who helped develop the series, said the episodes currently being worked for next year will be "vintage," in part because of the influx of new writing blood. And just in case that does not satisfy the apparently bottomless appetite for all things Simpson, Mr. Groening, along with Mr. Brooks and several of the show's longtime writers, are all hard at work in an office on the 20th Century Fox lot on the long-rumored Simpsons movie. "Part of the reason that we are still around is that there is a real emotional depth to these characters," said Mr. Groening, sitting in his office at 20th Century Fox earlier this month, a second-story hideaway on the lot that was denuded of the boxes of pop culture clutter - obscure world music CD's, knock-off "Simpsons" collectibles - that generally surround him in order to create enough space for an interview. "And I think there is a relative lightness of sprit over at the studio," he added, with a laugh. "They seem pretty happy over there."