Ah, it's easy, mate. Most recent posts are at the top of the page.
Seriously though, moderators do not have that power. We can delete posts or even entire threads but major changes to the structure of the forum have to be done by the owner. And the format has to allow the changes. Giving threads a 'shelf life' would be a major change. Do you have an example of a problem you would like to see addressed?
Country is a state of mind, not a state of America.