I was going through some old Dallas stuff on the internet and started watching old 3rd season episodes particularly A House Divided (the season finale where JR pulled that one big swindle causing all of Dallas to hate him and one to actually shoot him created the biggest whodunit ever for a soap opera) as it had Jim Davis on it playing the Ewing Matriarch along with other great story lines and character connections. Dallas was at its prime and had the best story lines the first four seasons.
Many say it was Patrick Duffy leaving in the 1985 season that killed the show as the ratings never returned even when Duffy appeared that one season finale in Pam's shower to stay on until the saga ended in 2012. I say it went dead after the incident when JR and Bobby both had the contest given to them to see who gets Jock's inherritence. That and with Barbara Bel Geddes appearing in fewer episodes in the latter seasons as her health was bad caused the show to lose out.
Then when JR went to prison in the Hillbilly State (although writers never specified which state it was, we all can guess clearly which one it was) just for sleeping with that girl Calle (whom he later married) was real bogus. I mean he did not even do anything mistameanor and it was just an act people do every day, and yet he went to prison without even a proper trial and reprensentation. Despite there are some ultra conservative cops and counties in our nation, that still was real dumb even for TV writers of a bizarre drama show. Then JR busted out and forced to be a slave like it was the old old old south, even for a criminal like JR that was way too much.
All In The Family was another that was better in the first five seasons than those following. When Mike and Gloria moved out the show, although still all right, was not the same as when they all lived together under one roof.
Hunter, was one where once actress Stefanie Kramer left, the show took a nose dive, which maybe why it lasted only one season after her departure.
The A Team, was even a big disappointment in its final season after the CIA caught them and forced them into doing spy work in other countries over the show's original premise of being mercinaries helping typical folks with problems the cops could not handle. That was the worst turning that show around the way they did as it was best when they were working for just plain people fighting domestic crime.