Why can't we access "archived" listings?

Anna, the archive is only available to Trademe themselves and often with classifieds once it's expired, it's gone for good. It's best for any listing to create it first in a word processor or text file so you have a copy, or, once you have created a listing, save the whole listing by right clicking and Save as - webpage complete. That way you can easily copy/paste from that to create a new one at any time.

I don't suppose it would help with this kind of listing but you can sometimes access archived listings in my products via the photos section. 

If you create a new listing and click 'Use Existing Photos' you can search for the filename of the photo you used in the listing (or if you don't list much just scroll through until you see the photo). Then click on the image and then 'use photo'. Once the image is in your new listing click on it again. On the right of the window that opens is a list of 'Other products using this photo:'. Often the archived listing will be included in the list. You can then click on that link and open the archived listing. If you want to relist it you can click duplicate.