IIRC it’s something like 20? You can just try it yourself, though. Go to the middle of a thread and refresh the page, then check the network tab for the request, or just count the elements in the DOM. it’s different if you’re at the start or the end of a thread, however, or if the thread is just short.
You probably shouldn’t need an exact number anyway. What do you want to do with the posts?
I’m trying to change all the text in all the posts for an April fools thing (yes it’s early, I had the idea and wanted to make it before I forgot), but I’m trying to figure out whether it’s worth checking for newly loaded posts or whether just the initially loaded posts would be fine, since it’s a joke script after all.
Looking forward to seeing what you’re planning! Dealing with ajax is kind of tricky, but the effect is definitely better. I have a couple of scripts that modify all posts that you could look at. All of them are on the simpler rather than performant side, but they work well enough