You could see the fatigue setting in even before Bobby left:
- The silly retcon of the Ewing Oil origin story, now with Jason Ewing, and Jock legitimately buying out Digger and his never-before-mentioned brother (wouldn’t Jock have told Ellie this story at some point?).
- The introduction of the Ewing cousins (note to soap opera writers: cousin relationships are generally not as compelling as sibling relationships).
- Miss Elie’s dull new marriage, which added nothing to the show.
Although I don't view those things as retcons per se, there's no question that there was a bit of a pall over Season 8 -- which I attribute, if not entirely, to the recasting of Miss Ellie. There was a sense that something special had now been ruined.
Also, a series has a natural arc, and DALLAS' was probably seven years (Season 8 in TV talk)... 1978 to 1985.
I'd've hated to have missed Season 10 (although not the dream resolution which opened it). But Bobby's death, and the months leading up to it, had a finality about we even mentioned at the time.
But that was true about
all the nighttime soaps by the Spring of 1985 -- a slightly forlorn sense of ambivalent closure.