(re: I changed how messages get posted) one way many bulletin boards limit the number of threads displayed is to have the user specify how many days old the topic should be, with a drop-down menu that says
Only display messages from…
last 2 days
last 5 days
last 20 days
Then depending on what the user has selected, only the topics from that number of days are displayed. Don’t know if it would be worth implementing here, but it’d be one way to go about it. It could muck up the pages where there are fewer posts, though.