I prefer 40 per page, but definitely understand the 20 per page. What I don't get is this:
If a topic has fewer than 40 posts, it's listed for me in the forum as having only one page. When I click on the topic title, it takes me to the first page of the thread. If the thread has more than 25 posts, however, there's actually a second page to the thread.
In other words, I can't access the second page of the thread from the forum page: I have to go to the first page of the topic and click on page 2 from there.
It seems as if I've got a hybrid system: the forum page believes I have 40 posts per page, whereas the thread page actually only gives me 25 posts per page.
Does that make sense?
Daniel