Fraying on the string is normal wear and tear, nothing a little string wax can't cure. It is the broken strand of the string or harness that you would need to be concerned with and want to have the string and harness replaced. I had a bow for 9 years and when I sold it, that bow still had the original string and harness on it. I kept it waxed and soley used it to hunt with, I personally believe if you take care of them they will last a long time. First and foremost, change the string or harness if any strands are broken.