At the moment, we can increase it on our end, but it is a global setting affecting all users, including guests and bots. That puts a great deal of stress on the server and would bring the forums to a crawl (we did this once, for a few hours, and it caused many problems). So unfortunately, the answer to your question is no. Sorry
This is really a design flaw of Xenoforo, and it is really the most annoying thing coming to these forums. The main reason is because, stupidly, they refer to the page number in the URL, instead of having the message id in the url like pretty much every single other forum software does. Seriously, what kind of idiotic design choice was this?
So, if you were to change it now, the links would break
I saw some paid addons that offer the ability for users to have control, but, it seems to break other things.
I am just wondering, are we doomed for eternity with this software, or, are you opened to using other forum software?