tippy, once they go over 90 days the old listings will disappear, no matter where they're stored (except for things like turbolister).  I withdrew a lot of listings a couple of years ago because I wanted to push my other items more.  I 'stored' them by copying and pasting the title and description for each item into a notepad document, and the number of each item available.  I also have a code for each item so I put that in to identify the item and make picture uploading easier when I relisted.  I realised later it would have been easier to just copy and paste the HTML code for the description but it was still easy enough.  It's not for people with thousands of listings but I did about 50 or so and it didn't take long.