Before its fifth season in 1979-80, Laverne & Shirley was moved from the Tuesday-at-8:30-pm timeslot to Thursdays at 8:00. Its viewership fell drastically, from #1 to out of the Top 30. In an effort to improve its ratings, ABC moved L&S to Mondays at 8:00 in December. Its ratings at that timeslot fared no better, so at the end of February 1980, L&S was back at its old Tuesdays-at-8:30 timeslot.

Laverne & Shirley's average seasonal rating was above a 30 from seasons 2 to 4. What if ABC had decided to move Laverne & Shirley to Thursdays earlier, like, say, before season 3 or 4? Would its ratings on Thursdays have grew, declined, or stayed the same then?

Prior to season 5, I think the ratings would have stayed the same. The writers were just running out of stories at that point. Personally, I'd like to see all series end at S5, if they even make it that far. Writers would be able to go out on top and could wrap up story lines and give characters proper endings. If the fanbase was huge, they could always bring it back for a limited series, like The X Files is currently doing, or try for the big screen, or even a reunion show. Just my .02.