With emails we're sorted - you can archive and place emails into folders and keep them for as long as you like. I've been trying to think of a way to extend this to SMS messages too, and I think it could be done very easily:

At the end of each month the patch/application would generate a quantity of email messages each containing the SMS message history for a contact's SMS thread with an appropriate subject such as the contact's name and the date - the user can then choose to send the email to their own email account where it can be stored and accessed at a later date. The original SMS message thread should then be deleted from the phone which both frees up memory and ensures that there is no duplication in the archived emails.

Is this possible and is anyone interested enough to look into implementing a system like this?