Saving SMS archive in another location

Hi, I have been receiving notifications on my iPhone 4 that my SMS mailbox is full and that I must delete messages in order to receive new ones, as I do this however, my mailbox quickly fills again. I believe this is because I have an extremely long chain of texts between me and my girlfriend of 2 years. I understand the simple solution is to delete the thousands of texts, however I would really like to save them for sentimental purposes.

If anyone has any info on how to access this archive in order to save it in a .pdf or something, please let me know, as I have not been able to locate this information elsewhere. Thanks!

[Edit]-I am aware that there is a file location with a very long name where it is supposedly located, however this location is for pre-Lion, I have been unable to locate it using the same name now that I have Lion.

 

Thanks I'll give it a try! I was hesitant to turn to third party software as many looked a little on the shady side.

[Edit]-Just bought it, worked amazing, exactly what I was looking for. Thank you again, you just relieved a decent amount of unneeded stress from my life.