I frequent a few boards, and and some of them have a feature titled, " new posts".
it filters all the topics, and shows posts that are made in say the last few hours. it lists what board it is from, the thread title, etc.
its a good feature, that lets a user focus on the current threads that are in active discussion. It also introduces users to boards where they may not have normaly looked before.
older threads can still be accessed by going to the board and scrolling down.
that same site also has a feature, where if you read a thread and that thread has been inactive for 30 or 60 days, it posts a red font warning that it is an old and dormant thread. prevents answering questions that are long answered.