Can I edit articles that are older than 90 days?

You can access articles in the Editor and the Publisher via their IDs.
i.e: for 12up posts your URL will need to look like this:
https://mmsport.minutemediaservices.com/cms/editor/12up_en_international_web/01djgmhd3sch

To open any article using their ID, you must select the “All Time” option in the dropdown menu.