How can I backup or archive my iPhone messages? I'm upgrading to iOS 8 and need to make some room on my phone. Under "Usage" (in Settings), my "Messages" is over 2 GB. I assume this refers to the Messages app, including iMessages and SMS. I don't necessarily need to keep these on my phone, but I'd like to archive these for posterity. Are there any good ways of doing this? I would prefer to be able to restore messages to my phone at will, but I don't know what options exist. I've used Phoneview before and found its import/export functionality limited.
To keep old messages for posterity, I would perform a backup and then rename it so that it does not get overwritten. A quick google search will give plenty of instructions.

As regards to restoring individual messages to your phone, I don't know that it's possible. There are certainly a number of non-free desktop apps for both PC/Mac to extract and view items from backups, again a google search will give you what you need.