"I don't want to see all that old stuff cluttering my screen" or "I can't see that old stuff I wanted to see".
Either way - we can help you. Each individual forum (e.g. Class Association Business, Maintenance Topics,...) can be set by you.
Click on the forum you want to change the settings for and scroll down to the bottom. There is a dropdown labeled "Display topics from previous:" where you can select the date range. You can also modify the default sort order which is set to show the most recent post at the top. This is only a one time setting. If you want to change the default, read on.
Changing default age of posts to display and sort order: Click the dropdown arrow in the upper right where your login name is shown, then click on "User Control Panel" to open the user control panel (UCP). Click "Board Preferences" tab at the top, then "Edit display options" on the left. Scroll down and you'll see drop-downs for posts and topics that allow you to customize your desired display preferences (age of post, sort order, etc.). Change any settings on this screen that you want, then click the "Submit" button at the bottom of the page.
Remember if you only show posts after a certain date, you won't see these posts unless you either search for them, or change the settings again (either by the default settings, or individual one-time settings)