I don' t think I' d switch to synthetic unless your bows manufacturer says it is okay. You may find you can' t or the extra shock isn' t advisable. Usually if I see the coating on the cables slipping or if they looked nicked or frayed any then change them. If yo have access to a bow press you can do them yourself. I usually buy the cables and swedges from Lancaster Archery. Press the bow and take off only one cable. Refer to the other to see haw it' s installed and then put through the swedge. Release the press just enough to make the new cable taut and crimp the swedge. Now repeat with the other side. You can do one for a couple bucks instead of paying the pro shop $40.00 or better.