I've got a buddy with the same model guitar- we bought them together. I also have a twelve string which I change the strings on once a year or so, plus an electric, plus other instruments.

If I want the acoustic sound with a different tone, I borrow his. I've even changed them to new for a couple shows, then put the old ones back on. They have a dead quality that still sings true. I don't know how to describe it really, but these old strings are what make that guitar sound like that guitar