After reading my own comic in my phone many times, and considering most of the webcomic audience uses the phone to read, I've come to the conclussion that the best way to go without falling to the clasic-manhwa-infinite-lengh-style is to reduce the number of panels per page.
More panels means smaller panels, so it's harder to see what's going on if you are using a phone to read it. In this page, for example, the two top panels are very compressed, with less "air" than the rest. Since is only a dialogue between three characters that aren't doing anything isn't that troblesome, but on an action scene would be a fatal mistake. When the page is this small (I reduced the resolution on purpose) is harder to tell what's going on, right?

Webcomic format asks for easier to read pages, so I try to go around 5-6 panels per page. If I'm feeling playful then I use diagonal lines for a few panels and that's it xD