How Do You End a Campaign?

As regular readers should know, I am an advocate for long campaigns, so much so that I feel that RPGs are best enjoyed when played in that way. Even so, that raises the question: when do you end a campaign?

I think about this often, because my House of Worms Empire of the Petal Throne campaign is now several months in to its tenth year of weekly play, with a stable group of eight players, four of whom have been playing since March 2015 and one player who's played for almost as long. After nearly a decade of play, House of Worms is a perpetual campaign or very nearly so. There are so many character-driven goals, world events, long-term intrigues, and meddling NPCs to provide us with another decade's worth of play should we desire it. Whether that will actually happen is a separate matter.

More than likely, House of Worms will end much sooner than that, probably for mundane reasons, such as players having to stop playing due to real world obligations, changing schedules, etc. If so, it's quite possible there will be no "end" to it. Instead, it will simply stop in medias res. Would that be a bad thing? Would it be preferable to arrange something more conclusive and, dare I say, more satisfying? I'm honestly not sure. On the one hand, putting a proper cap on the campaign might feel better, in the sense that no one involved will have regrets about things being unresolved. On the other hand, I worry that such an approach borrows too heavily from literature or drama, which are very different kinds of entertainments from roleplaying.

Most of my past campaigns, both recently and in my youth, simply ended, usually due to boredom or distraction. For example, my Riphaeus Sector Traveller campaign, which I ran for three years, ended because I was exhausted and lacked the endurance necessary to run such an open-ended campaign at that particular time. The characters were in the midst of dealing with several different problems within the setting. When I announced I wanted to end the campaign, I didn't make an effort to wrap anything up; we simply ceased playing. No one involved seems to have minded, but I must admit that I occasionally think back with some regret on how abruptly the campaign ended. Of course, I'm not sure how I could have wrapped things up, since it was, as I said, a very open-ended campaign without a single contrived narrative. 

I'm curious to hear what others think about this. I'm especially curious about others' experiences of ending campaigns that have run for a lengthy period of time (a couple of years or more). Did they end because they'd reached a natural stepping off point? Boredom? Real world issues? Did they end because there was a decision to end them? If so, how did they end? Did they simply cease or was there some kind of resolution? If there was resolution, was that resolution a consequence of prior events or was it engineered in order to provide a sense of closure? 

This is a topic about which I'd really like to know more, so please share your experiences, stories, and insights, if you have them. Thanks!