Is there a way I can set the time limit on the display of the forums?

I have a new site and the forums topics are dissapearing before a reply gets posted. I would like to alter the time for guests that the topics are displayed for.

Also I would like 2 blocks that showd the last 10 posts and the 10 most popular topics, even after the time limit for displaye dposts run out.

Any help on how to do this would be most welcome.

thanks in advance :)

Anyone?