My Hoyt manual says "under normal circumtances" replace the string evey two years. I am sure the other guys here will have more to say. What is normal, I donno. I shot my Jennings for 4 years and I can no longer get 70 lbs. I just noticed after not being able to get 70 lbs that the ATA is no where close to specs and I ordered a string. There are a couple of guys here that make strings who I am sure will give you a more tangible answer.