[chrishajer]

There’s no equivalent that I know of for bbPress. It would be the equivalent of a WordPress blog post page, where you want 9 posts (for example) listed as a default, but if there is a long post, some sort of limit kicks in. I don’t know of a way to do this in WordPress at all, other than limiting the number of posts on a blog page, or with a custom query. The nextpage tag only works on a single long post. It’s possible you could change the number of replies listed in bbPress when it encounters a long post with a tag like that, but I haven’t seen anyone do that yet.