Nearly unique among TV comedies, the program has no laugh track because canned guffaws would occupy airtime that could otherwise be used for dialogue. Every episode takes about eight months from conception to broadcast, and during that year every script is painstakingly fine-tuned and rewritten by a team of as many as 20 writers. And although they are almost surreally dysfunctional, they love one another in the idiosyncratically complicated way that real family members do. They can quote long stretches of dialogue from memory and identify uncredited guest appearances, such as that of Dustin Hoffman, who supplied the voice of a substitute teacher. The Simpsons is now in its ninth season, but to me the show doesn't seem tired.
Animation is a blessing in that regard.
Leave It to Beaver declined irretrievably when Jerry Mathers hit puberty. Bart, in contrast, will never have to graduate from fourth grade. The show will last until viewers' tastes change or the writers lose interest. I hope that doesn't happen for a long, long time.