Indeed. Putting David and Maddie together on Moonlighting kinda jumped the shark for that show, as well as Major Nelson and Jeannie. I'm sure that there are others.
It's been many years since I read Adriana's Collinsport Chronicles, so my memory of this may be a little spotty. Julia finally gave up on Barnabas and married another doctor who was about the same age. Only to find that Barnabas' next fixation was a local woman of about Julia's age. Julia's husband did pass away at one point but I dont think that Barnabas and Julia ever got together.
I neglected to mention that Sheriff Patterson never got over the loss of his long term partner Dave Woodard.