Interesting point, but I have to disagree. At the time, the Disney model was to re-release their dozen or so classic movies every 7 years, keeping them out of the public eye otherwise (except for rides at the nation's two premier tourist destinations, of course). No VHS/DVD release, no continuous playing on TV. It helped make the films timeless, and allowed each new sub-generation to re-discover them.
The Simpsons are on TV constantly--new episodes on Fox and seemingly endless repeats in syndication. They never go away. Moreover, being at its heart a parody of American life, it's far more dated with constant pop culture references. And less face it, it was made on the cheap--it was never meant to have the artistry of a Disney movie. I still make it a point to watch every new Simpsons, but there is no way the show or its characters will hold up like, say, Cinderella or Peter Pan.