I know around the 15th or 16th season they started to have in jokes on the show about how it should end. I think Smithers opened a door into the simpsons dining room while they were having dinner shouting "MR. BURNS HAS BEEN SHOT....AGAIN....BY MAGGIE!!!!" Then he kind of just leaves. Then the family say something like "This is really getting old. Someone should put a stop to it."
Also, I really enjoyed Family Guy when it started so seasons 1-3 are really good for me. Anything post cancellation is garbage.
That's why I'm really worried about the new Futurama start up.
There has only been one joke from the post-cancellation seasons that has truly made me laugh and it was this one.