On leaving Cheers.
I cant understand how anyone could see it as a bad thing that Shelley Long left Cheers when she did. If you watch the DVDs of seasons 1-5 now, the Sam and Diane plot had well run its course by season 5.
They'd explored every possible facet and possibility of that dynamic, anymore would have just been repeating and the only place left to go was have them marry and in "most" cases even the most casual sitcom viewer will agree thats the death knell, when the shows focus has been the love/hate relationship.
The alternative would have been another season of them bickering, well written bickering, but still just the same thing and after five seasons of such consistently fresh, well written comedy, any sign of repeating and just grinding it out would be the mediocre footnote to what had been so very good.
I dont care to speculate on Shelley Long's personal motivation for leaving, but by default or design it was 100% the best thing for the show, because it reinvigorated the series and i feel gave it six more seasons it either wouldnt have had or wouldnt have been as good, had she stayed and just trod water so to speak.