Is 'mark forums read' automatic?

Does this happen by default? On another local VB based forum I visit if I return after some time and hit the new posts button I get this message:

The threads below have not been updated since your last visit but still contain unread posts.

Is there a setting I can adjust so that threads I haven’t visited stay on the ‘new’ post list even though I’ve visited the site? I looked in my settings and didn’t find anything.

Thanks,