Do I have to do each one individually, or can I do several at once? I don’t want to clear them all out, just a few old ones.
You have to unsubscribe to threads individually; there’s no “batch” option.
Go to your user control panel. Look at your list of subscribed threads and select the proper time frame from the pulldown menu on the right. Then simply click the “unsubscribe” link on each thread for which you wish to cancel your subscription. After clicking, you will be momentarily taken to an information screen and then bounced back to the subscribed threads list in the user control panel where you may repeat the process until you’re done.