We are thinking of switching to Confluence from Twiki. One thing that seems to be missing is notification for out-of-date pages. We use this heavily in Twiki. When you edit a page, you get a few radio buttons at the bottom of the edit page where you can select how long a page is valid for before it becomes out-of-date (a week, a month, a year, etc).

When a user visits an out-of-date page, there is a warning at the top that the page may be out-of-date. As well, the last editor of the page receives an email periodically saying which pages are out-of-date.

I have attached an image of the bar that appears at the bottom of the edit page in Twiki.