  I'm a pretty big Simpson's fan and watch the show pretty often. I usually have about 5 episodes stored on my DVR that I pick from daily. If you think about it, most cartoons will "reset" each episode. Someone dies, they come back the next time, much like Itchy and Scratchy. However, the Simpson's have events that don't reset. And there are some items that are even carried through and recognized in other episodes.
You never hear Fred Flintstone talking about how his car broke down in a previous episode. Below are some sticking events that I can come up with. Flander's wife Maud stayed dead. Milhouse's parent's stayed seperated. Homer remembers every job he's ever had. Homer refuses to admit he ever had a snow plowing job, which he did. Marge retained the elephant and some of the props used for Apu's wedding. Anyhoo, there are only about a million examples...these are just what I can come up with on my way out the door for some dinner. Let's just hope it's true, "Never fear, we've got stories for years". 
