If your string stretches so much it affects your kissers anchor it is defently time for a new string and cabels. I have never had a string stretch so much it affects my draw lenght or anchor points. If you want to know if your string is stretched measure your axle to axle length on your bow and compair it to the factory specs. That will tell you right off if it has stretched.

It is good practice to replace your strings and cabels every year at least once or even twice depending on how often you shoot.

Winners choice is a good way to go. Not sure of the price for a matthews though.