You probably don't want to read every single thread and are wondering how we know there has been a new post ......... The speach marks in the little box on the left of each thread on the home page turns orange when a new post has been made.
If you click Mark all forums as read at the bottom right of the home page you will notice the little orange icon will disappear at the side of each thread, this will then only turn orange again when a new post has been made making it easy to see. The orange notification will only disappear again when you have read the post or click on Mark all forums as read again.
The orange notifications will let you know when new posts are made you can then search or read the old threads at your own leisure.