As @yondoloki said, the key benefit of working on long form storytelling is the reader loyalty. It's the payoff for all the hard work you'll have to put into designing and drawing all those unique props, characters and locations, setting up character and story arcs, wading through exposition, choreographing fight scenes etc. In the end, it's worth it to me.
And the thing that's great if you're doing Fantasy with loyal readers is definitely that the generally pretty distinctive character designs lend themselves to fan art. The comic I'm drawing now is pretty new:
But it's sort of a reboot of an older comic I did years ago, which had a small, but really dedicated base of readers, resulting in... FAN ART. Glorious Fan Art!
A big thing that spurred me on to reboot was a pro artist friend drew the main character last November just on a whim... like years after the comic had gone on hiatus, he randomly did this:
And I thought.... "These characters mean something to people. Even now." I was an idiot in my twenties to not realise how rare and valuable that is.
So yeah, long form fantasy... it's a slog, but it's so worth it.