Please review our Message Storage and Data Retention Policy. Depending upon your account, you may have gone over your limit for storing older messages. I would highly suggest backing up all messages using a Cloud drive or something along those lines :)
If you want to use RC Archiver you can read more about it here. However, if your account is not eligible, you would simply have to manually download information and place it in your preferred cloud drive.
That is what I am asking about - documentation for downloading the datastore to our Cloud Drive on Google or even to our local storage. I cannot locate documentation on the procedure for how to do this for text message records.