The Campaign for North Africa is probably the most extreme example of this.
https://en.m.wikipedia.org/wiki/The_Campaign_for_North_Afric...
A "proper" game requires 10 players and an estimated 1500 hours.
Which I guess makes it a game only in the theoretical sense.
Today any group playing it is more likely to play it using (the open source tool) VASSAL (here is the free module to download to play CNA: https://vassalengine.org/wiki/Module:The_Campaign_for_North_...). I saw a thread on a wargame forum just a few weeks ago looking for players to start up a new game. Playing online probably makes it a bit more likely to be played (but also less fun than to gather around a huge table IRL?).
(Aside: By tradition, an old "gentlemens agreement", between the wargaming community and wargame publishers, when playing a game online with VASSAL every player is expected to own a physical copy of the game. You are not supposed to download the CNA module to play it for free without owning the game. There is no DRM or other attempts to police who plays what, but as long as the system is not abused too much the publishers are happy and most keep allowing those tools to exist. It is a nice contrast to how copyright is handled elsewhere, including in more mainstream tools for playing online boardgames. I guess it is only possible in a small niche hobby like that, and possibly only because the tradition started last century before there was big money in selling digital versions of boardgames.)
I think you might be under-estimating how long a 1500 hour game is. A person who works 8 hours a day works 2000 hours in the course of a year.
And if the game's in-person, there's travel time - it's not like a computer game where you can do a 1-hour session every evening for 4 years.
Even a the longest RPG adventures like "Dungeon of the mad mage" (famous for people getting bored without completing it) tend to be less than 500 hours.
https://edition.cnn.com/2020/09/20/us/dungeons-and-dragons-l...
(A bit extreme maybe, but I heard of shorter campaigns, but still lasting for at least a decade of regular play.)
And I think you underestimate how dedicated some people can be to playing games like CNA. It is a big game, but it is not absurdly long compared to other big board wargames.
Here is a BGG thread from 2010 (well before CNA became a mainstream meme?): https://boardgamegeek.com/thread/580214/
Note how the thread starts out "25 years after playing my last game of CNA".
So called "monster wargames" was a trend around 1980, toward the sudden end of the era of board wargames being almost-mainstream. I do not know if CNA was the biggest of all, but I think not. It was part of starting the trend, but later games were probably bigger and longer.
https://boardgamegeek.com/geeklist/42904/the-biggest-of-the-...
One of its flaws is that it makes you, in the role of the commander (or one of five commanders, anyway), keep track of:
> "[If using the full rules] every individual plane and pilot in the three year campaign."
This is madness! A real commander wouldn't keep track of this, so why must the player? This level of zoom-in is typical of tactical wargames, where it makes sense, but it's nonsense for traditional "cardboard" grand strategy wargames without computer assistance. So it makes total sense that playing this would take more than the actual Campaign for North Africa, since in the real deal those commanders wouldn't track every individual plane.
I don't think this was made to be actually played, and I struggle to believe anyone has actually finished it, regardless of some internet claims.
P.S.: related :
https://www.filfre.net/2020/01/master-of-orion/
> [...]
> Because getting seven friends together in the same room for the all-day affair that was a complete game of Diplomacy was almost as hard in the 1960s as it is today, inventive gamers developed systems for playing it via post; the first example of this breed would seem to date from 1963. And once players had started modifying the rules of Diplomacy to make it work under this new paradigm, it was a relatively short leap to begin making entirely new play-by-post games with new themes which shared some commonalities of approach with Calhamer’s magnum opus.
> Thus in December of 1966, Dan Brannon announced a play-by-post game called Xeno, whose concept sounds very familiar indeed in the broad strokes. Each player started with a cluster of five planets — a tiny toehold in a sprawling, unknown galaxy waiting to be colonized.
> [...]
> In practice, Xeno played out at a pace to which the word “glacial” hardly does justice. The game didn’t really get started until September of 1967, and by a year after that just three turns had been completed. I don’t know whether a single full game of it was ever finished. Nevertheless, it proved hugely influential within the small community of experiential-gaming fanzines and play-by-post enthusiasts. The first similar game, called Galaxy and run by H. David Montgomery, had already appeared before Xeno had processed its third turn.
> [...]
I think it's different to CfNA in that this game simulates an actual campaign with clear goals, but that endgame cannot be reached in a reasonable time by any owner of this piece of cardboard. I'd say that's bad game design...
Sandbox doesn't mean no end goal(s), though you typically get the option to continue playing past the end goal(s).