The "fingerprint" does change over time.
It must be remembered that firearms are made of metal, as are the bullets. Over time, the friction of the metal bullet traveling down the metal barrel causes wear to the barrels lining. Even cleaning the bore, something I do with my firearms after every outing, will do the same thing since most cleaning kits come with wire brushes.
My Glock model 20 has been fired over 1000 times since I've owned it, so its fingerprint now would be different than when it was new.