UBB.threads PHP Forum Software Community Forums Resources and Customizing How Do I? Post Island - time limit

I've created a forum for events.
It's not publicly viewable.

I've created a Post Island (New Topics Only) to display just the headline so people can then choose the event they want to view.

As the event post gets old the event vanishes (I think this is the reason).

The problem is, some events may be six months away - how can I keep them in the post island?