I've just bought myself a pair of Beal Iceline 8.1 ropes. They are in great condition; I've inspected them for all the obvious bits and pieces and they seem to be as good as new! I know the guy that has sold them to me; he seldom climbs and says he hasn't ever taken a fall on them.
That aside, he's said the ropes are "about 10 years old". On the Beal website it says a rope should be retired after 10 years.
Why is this? And how long have you been using your ropes?
In reply to The Lemming: the creaking noise is usually chalk and can be sorted by washing.
To the OP , the materials ropes are made of are quite stable if stored in a dark,dry, room temperature environment away from the chemicals that harm them (acids, certain solvents) There is no reason if a rope has been well stored that it should deteriorate to a point it should be retired.
In reply to A Crook: That's fantastic news, you will have a busy day ahead of you informing Beal, Edelrid, Edelweiss, New England Ropes (and others) that they have incorrect information on their websites ;0)