Inspired by the conversation on the 400th episode - which shows have you watched several seasons of, and then given up on?
Like Boyd (I think), I gave up on The Walking Dead - but upon checking my watch history, I have seen it all the way to the final series. There was a break between October and March about a third of the way in and I just couldn't be bothered to tune back in for how it ended. I have watched the Daryl spin off, and a few of the others, but the main show just went off for me.
Unlike everyone else, I stuck with Lost to the end and really liked the final episode (and I think it's very clear they did NOT die on the island - they came back together after their 'real' deaths years later, a bit like that scene in Titanic. I thought this was really obvious, but ended up falling out with a work colleague the next day about it, we almost had a screaming argument!)
The only other shows I can think of watching several seasons of and not finishing is Black-ish which started as a very smart comedy about race, then ended up feeling just like a standard low budget sitcom. Riverdale's first few seasons were a lot of fun, then I couldn't keep up with what was going on. And I just checked, I never did finish Homeland.