There are a few ways to use "thread memory" as you call it. When new information is posted, the thread will have a "new" button next to the name. It will also say what the latest post was and by whom. Clicking on either the "new" button or the latest post (but not the person) will take you to the oldest unread post in the thread.
Oh my goodness, I had no idea it would do that if you click on the "new" button! I guess I never tried that. That is so much easier. Thanks!