I replaced the string on my Parker Phoenix EZ-Draw bow after 1 1/2 years as the cable frayed from a burr on the cable slide . I figured as long as I was doing one ,I might as well do both .
Check your string and cables for wear . Keep the string waxed and every few times ,clean the old wax off the string as it will pick up dirt & grit .
If it's not broke , don't fix it ........unless you are nervous about the reliability of the string .
Most "quality" strings are pre-stretched .