Yeah, as the others have already said, consistency is by far the most important element of a serial's update schedule.
But I've been kind of surprised about how long certain segments of the serial audience want chapter to be. Before I found this place, I always assumed people would want something short. Back when I was doing nonfiction blogging (It feels strange having to specify that a blog is nonfiction, but that's another topic for another day), the rule was to make a post as short as possible while still conveying some level of value.
That's actually changed in the past couple years, with blogging platforms like Medium encouraging longer posts, and sites like Buzzfeed creating quick-to-read but still somewhat lengthier posts (24 GOT Gifs That Show How I Feel About Mid-Terms, or whatever).
Still, the length web serial readers want can be loooong. I don't remember the specific numbers, but a while back I was doing word counts for some of Wildbow's posts to get an idea of what a successful web serial's posts looked like, and the word counts were like six or eight thousand words?
Thing is, no one in his audience complains about it! And then they pay money to have him write a third six-to-eight thousand word chapter some weeks! Feels kind of like smart Hyperpulp -- Walter Gibson on crack, or something. (Not that I'm saying Wildbow smokes crack. I'm just saying it would make a lot of sense.)
Post lengths seem to be getting longer here. We've moved from the less-than-one-thousand-word posts of Superguy (which I enjoyed in an ironic but nonetheless joy-filled way -- thanks for the link Jim Zoetewey!) to the many-thousand-word posts of Wildbow.
We have yet to reach the upper limits of what a web serial audience is willing to read, which fascinates me. I think you might have to have multiple people writing the same serial before you burned the audience out content-wise? Which I'm not saying should happen. I'm just kind of theorizing here.
Anyway, I'm not exactly someone you want to model yourself off of, but my posts tend to run 2,500-3,500 words. I'm happy with the schedule.
Of course, the length OR consistency of the posts doesn't really matter unless you bring a minimum level of quality to bear. I'm not even talking about writing -- I'm talking about storytelling. If you're able to write interesting characters, and you're able to have them do interesting things?
I think the audience will follow you anywhere, no matter how long or short your posts are.