Save old emails for later use

Scenario: I want to remove all emails from before 01012007 because my Inbox has become bloated, but I do not want to delete them permanently if I later have need for one or more of these old mails, I just want to keep them somewhere safe.

I know I can save a copy of my "Profile" folder, but if I later copy back the relevant email folder, it will delete my present email folder, so I need some form of "re-aapending" my old email folder to my current one.

And yes, I have considered copying the whole PTB folder, deleting the most recent mails and have a separate PTB just for old mails, while keeping my current PTB with just the newest mails, but I'd hoped there would be an easier way?

Any ideas anyone?