This is one of those things that seems like it should be easy, but in fact requires much testing to ensure a change doesn't negatively impact the site.
Having said that, it's on the list to be tested - I'm just not sure when.
Now, as someone who also prefers to view as many posts per page as possible, I have a little workaround you might find interesting. The archived version of each thread actually displays 250 posts per page. To view the archived version of any thread, all you need to do is change the url a little. For example, the url for this thread would be changed from:
Code:
http://www.flyertalk.com/forum/suggestions/1093982-view-all-posts-thread-pagination-off.html
to
Code:
http://www.flyertalk.com/forum/archive/t-1093982.html
The downsides? Appearance isn't as polished and you can't post a reply from the archived thread page.
Still, it can come in handy when all you want to do is read a long thread.