For comics or novels?
I feel an episode has to be able to cover a story beat (a good pausing point within the story). During a story beat, development has to be happening.
Is a conversation happening? Did a character discover something? Something along those lines.
Now, how many pages that is can depend. For some people, only one page is enough. For others, they might need 2-3 pages. And then you have people (like me) who might do pages along with long slabs of panels.
So it's important to look over your pages and decide "which place can I pause for an episode?". Sometimes, that can vary how many pages you post for a single episode 
I don't know too many comics that have long episodes. That would be a lot of work I'd think! But since I write novels I can only really speak to that. I keep my episodes between 900-1200 words (5-6k characters). The general audience seems to prefer shorter episodes, so some will keep theirs to 500 words. Really, it can vary from reader to reader.
But like @DiegoPalacios and @Jenny-Toons said, the progression of the story is the important part.
A scene is defined as events which involve specific characters, place, and time. Whenever two of those three elements change, you have definitely moved into a new scene. Traditionally, one scene per episode is what we expect. The general trend in literature, however, is to move towards shorter episodes. Despite moaning of lessening attention span, this trend has little to do with that and more with practicality. Tapas probably likes shorter episodes because there are more to sell individually (and thus the scant 500 word minimum per episode requirement during Writers Camps). Audiences might favor shorter episodes because reading a quick update can get squeezed into a short break in a busy lifestyle.
I have been trying to shorten my own chapters by breaking them up when feasible. On the other hand, I have been also combined two short scenes in a single chapter in order to set up a joke and then deliver the punchline before the set up is forgotten.
In novels, 3000 words or more in a single chapter seems to be pushing my luck.
I'm not sure if I'm the right person to answer this, as I'm more used to (and prefer the format of) physical books or comics that allows longer chapters.
For me it depends on the content, I wouldn't mind 5000+ words or 50 page something chapter as long as the thing happening interests me and had to be done. But yeah, as many have stated before, mostly webcomic and webnovel readers are on the go and reading in small device thus they prefer shorter chapters.
I think I'm guilty of making longer chapters... But well 500 words? What can I convey with that? I envy you who can write short.
And for me somehow doing the "Chapter 1: part 2" kind of unpleasant to see and keep track of, I'd rather make it two different chapters.
Before Wattpad I wrote 5000 words per chapter, before Tapas I wrote 3000 words per chapter, and after Tapas I write 1500 words per chapter.
About 3-5 minutes of read is recommened, 10 minutes max, and over than 10 minutes is too long.
It's based on the reader's attention span, kind of the same rules as youtube videos.
You can set a timer and start reading your comic/novel to see how much time it took to read yours.
yup! its not abt length, its abt pacing
notice when you read a novel theres no episodes, but lots of places to stop - scene breaks, chapters. you notice when youre really enjoying a book, you stay up that extra 30 minutes at night to read the next chapter? thats bc theyve weaved a structure that keeps dropping in things to look forward to, questions to be answered - scenes are ended just before they get good, so you keep reading to see the climax in the next scene
when im writing i like to keep in mind this piece of advice from taika waititi, who says that the second hes bored of writing something, he moves on to the next scene. mid-sentence even - it can be cleaned up later. while youre the writer, youre also the audience, and if youre enjoying yourself you have to trust that its enjoyable. and if youre not, dont write that bit. (that said some things you enjoy as a writer should be cut bc they wont be as interesting to the reader for various reasons)
that said, for tapas short bursts are the norm - people are reading on the go a lot of the time, so id say 2-5 pages of comic is a good length. not because longer could get tedious, so long as its well written, but bc 10 page updates can feel intimidating before reading, especially when compared to a norm of 2-3 pages. (though for infinite scroll thats a lil harder to calculate :U)
For comics, I like long episodes if that means the story is advancing. This is especially true if the author doesn't update often, then at least I can get something out of the update and not feel like I waited a month for nothing.
For novels, it really depends on the narrative style. Some people can make long chapters that still keep me hooked, whereas others can in few words tell enough and we can move on to the next chapter.
It's a lot trickier to figure out on infinite scroll, but I've try to split mine by scenes, which usually lasts around 10-20 panels. If it's a longer scene, I try splitting it into conversations sections, if there's a major subject change, or a new person coming into the conversation. I feel that's the right mix of moving the story along vs small regular updates.
As I reader I've been reading the webcomics that update only a page or two every week, and had to read conversations that go on for months because progression is so slow. It takes some skill to make a page a week work and not drag on imo. It's a very delicate kind of pacing.
My episodes are split by scenes too, they're usually 20-30 panels, if episodes go way over the 30 panel mark I sometimes split them in half and upload separately. As long as I feel like some sort of progress has been made in the episode I'm happy.
Yeah I'm honestly more bored by this than by episodes that are too long. An episode that's too long might just be the only badly paced episode in the series but a conversation that's slugging through months of updates is really boring to read week by week. I usually ignore updates and read all the pages at the end of the month or something.
This is how most webcomics are though, and pacing is really hard to do especially if you need to get a conversation scene out of the way so I understand.
I feel like about 1500 words to 2k words is a good episode length for a novel. Any more than that, I feel like I don't have time to finish the chapter/episode before I have to move on to the next task of my day. Or I feel like I'll lose the attention of my readers. Lately, I've not come anywhere close to the 15k character limit. I discovered that's actually closer to 3k words. 
I typically don't mind (comic) updates that are all the way up to 1 chapter (so like 10-20 pages) because that's what I was used to reading growing up with comic books and manga volumes. For web comics though I almost feel like more than 10 pages in a single update could get cumbersome.
(then there's my output as a fledgling newbie comic artist who can only do the "1-page-per-week" thing xD;; I look forward to being able to increase my output someday...)
Like people said, I agree 'tedious' has more to with the pacing than the length of an episode. However, 'overwhelming' can be a problem with very long episodes even if the pacing is tight. Tapas doesn't save your place in the middle of an episode, and a lot of people don't like reading more than a certain amount without a save point.
18 days later
Just yesterday, a friend referred me to a web-novel that he was enjoying. It's 450,000 words. It's on-going. It's Book One of a series. It has one main character in a wake up in a new world scenario.
By comparison, War and Peace has a little over 500,000 words, features hundreds of characters, and sort off tells the story a society across two political eras.
Sorry Prolific Author, my life is just not long enough dedicate a large portion of it to consuming one story which may or may not ever reach a conclusion. Regardless of pacing, regardless of ease of reading, you should not need over a million words to tell a single story.
I'm mildly embarrassed to say that I've read stories like that in the past. Most of the time though, I caught them early when there were only a handful of chapters and I just kept going as it was uploaded.
I think though, as a writer, that is definitely way too long! There is no reason that "book 1" in a series needs to be that long. That's an entire series by itself for Heaven's sake. You need to be able to tell a cohesive narrative in a fraction of that word count.
I print each full episodes into a hard copy comic book. So, I have to think about cost a lot, since it is in colour. So, I tend to confine my full episodes into a set number of pages (18-26 pages). The episode always has to end on a cliff hanger, so I have to condense the plot into different sections. That requires re-writes sometimes if the plot runs longer, which happens sometimes, I also make sure that the story doesn't drag too much, because of the page constraint, every panel moves the story forward in some way.
As far as comic episodes go, the fact that I print it helps me reduce the story from running too long.
