What kinda vertical comics are you reading? The ones I read don't take that long, nor do they have anywhere near 90 panels on average (one possible exception being Denma, though I've never counted).
Now I wonder if the screen resolution is a factor. I'm on a 5k display, so I see quite a bit of content in a single screen. Maybe viewing on a smaller resolution creates that "ahhh when is it going to end?" feeling. Though I never experienced that feeling even back when I was on a 2560x1600 display?
I also don't see anyone complain about monthly magazine manga chapters (those have like 40 pages) being too long? Although that could be because you can remember which page you leave it off, I always read those in a single sitting and assumed (perhaps incorrectly) that most other people did so as well.
That said, here is one example I can think of that has way too much white space even for me. It doesn't make me wonder "when is it going to end!???" This comic's chapters don't have a lot of content (something they get complaints about all the time in their comments section), so the chapters feel short to me. It still messes up the sense of timing, though, which is why it's too much for me.
Interesting. I first came across Korean webcomics on a manga scanlation site, where they divided the chapters that way. And I found it severely annoying. XD;; I wanted to A) scroll a lot OR B) keep clicking for the next page without scrolling. I didn't like having to scroll a little, then click for the next page.
The main reason I make mine that way is because I wouldn't be able to update often if I were to make my updates longer. I try to make my updates a bit longer than the chopped-up scanlation I came across, though, because that was... really annoying. It was like reading a traditional page comic that was just a little too big to fit in one screen, which I dislike as well. If I have to click often, that's enough work for me... don't make me scroll on top of it!
Different strokes for different folks, I guess.