Indeed:
which I hoped to elucidate with a short history of long games above. I think one really standout element of Rebels and one thing that contributes to length (but could be more efficiently done now with multireplace) is the hard binary choice of helot or not at the start of the game. This kind of binary choice is something we historically discouraged in our design because for one thing it can lead to a game becoming so long the author can’t finish it (but you did!! 
).
BUT. Jason floated a theory recently that if done in a certain way, these kind of hard branches could become more common because players truly enjoy them. I do think they’re easier to do and manage than we perhaps initially thought. And that would certainly lead to longer games.
Also, I think it’s important to acknowledge that long games are really very differently designed and hence are longer for different reasons. Kyle Marquis’ games (Empyrean, Silverworld, and the upcoming The Tower Behind the Moon which is a charming uh 395k, I think) are long for Kyle-ish design reasons. He’s also, like @gower, a bit of a prolific maniac, but even so, just speaking of Tower: you can play as like one of six different types of archmage…and believe me when I say there is custom text for each type of archmage. The game is just bound to be longer because the author is offering choices that matter, in the sense that the game is responding to your choice to play as a vitalist archmage or a necromancer archmage and giving you an appropriate experience as such.