What's funny is that the simpisons has been on so long that the "good legacy years" keeps getting extended while people's memory of those episodes keeps getting exaggerated. I vaguely remember back in the days of dial-up when the Oakley/Weinstein episodes were airing people were arguing "they were too slow paced" and "they aren't as funny as David Mirkin's".
The Simpsons has only had one kind of akward phase (the Mike Scully years), and that ended 7? seasons ago now. No all of the new episodes are not great, yes 20 years of traditional plots have left recent plots a little wacky, sure continuity is often laughed at. The world of the simpsons, however, has remained remarkably consistent for going on twenty years now. The writing staff has remained remarkably intact, the characters are still written (mostly) the same, and the show remains remarkably clever in spite of it's age. There haven't been any shark jumping plot moments, (not even the movie). I feel if there was an appreciable drop in quality it would be one thing, but I personally just don't see it.
I feel that most of the concern about the show remaining on is fear that the classic 20 year old episodes will be forgotten or thought less of if there ever is a genuine drop in quality. If anything, I think the opposite is true - people seem to have forgotten that there were alot of poorly written, crudely drawn episodes especially in the first 2 seasons. The Simpson's legacy in terms of cultural impact and television influence will always be intact.
I certainly understand the argument of ending a show before it goes on too long. I just think the Simpsons (so far) has been mostly an exception to the rule. As long as (most of) the original creators are still involved***, they keep hiring talented writing staff members, and they keep wanting to make more episodes - why not?
***Just a small p.s. I wanted to add regarding creators and original episodes. It's one of the most commonly held misconceptions, and a common argument against allowing the series to continue. Conan O'Brien was on the writing staff for ONE season order where he wrote or co-wrote FOUR episodes. That's it. While a comedy genius and responsible for four great episodes, Conan leaving (in 1993!) did not start the downfall of the simpsons unless "Treehouse of horror IV" "Marge vs. Monorail" "Homer Goes to college" and "New Kid on the block" are the only good episodes of the simpsons ever.
Thank you for allowing me to rant
