I've noticed a common point in nearly all the webserials I follow--in fact, all but one, now that I think about it: they are divided into relatively short "Arcs," usually labeled as such, which tend to be between five and twelve chapters on average. This seems pretty unique to webfiction, as I can't think of a comparable practice in other long-form fiction that I'm familiar with.
What I'm curious about, and would love to hear opinions on from more experienced voices in the field, is just how important is this to weblit? Obviously, every community has its little rituals and standard practices, and sometimes those are arbitrary and not all that meaningful. However, we can't deny that fiction on the web is its own kind of beast with very different demands than print or even ebooks, and the Arc format seems to appeal to one of the watchwords of online content: Brevity.
As I'm following currently updating serials, I don't find a whole lot of significance, if any, in the arcs. They're quite useful to me, though, in reading longer works from the beginning to either their point of completion or wherever they currently stand. It's a handy way to break up the story for when I've got time to read multiple chapters but can't afford to spend the whole day lost in a book.
Where this really concerns me is in my own story, which I've been updating thrice weekly for about a month now. There was a recent topic in this forum about series with multiple protagonists, and that's pretty much the boat I'm in. Right now I just have my primary group in one location, my little wizarding school in the Wild West, with a secondary plot and characters unfolding in another place. However, this is going to be a complex story heavy on the intrigue, and will eventually have upwards of a dozen plots unfolding simultaneously in various locations. I've considered focusing on one at a time for an arc of chapters, then rewinding the clock and using another arc to show what Group Two has been up to during the same period, but I quickly scrapped that idea as confusing and needlessly complex.
So I'm curious if you guys think I have made a horrible mistake in trying to publish this particular kind of story as a webserial. In more general terms, though, I'd also love to hear thoughts on the Arc phenomenon, why it works and why so many use it. It's certainly common enough that there must be a reason.