Fishing lines can definitely go bad. Certain lines such and monofilament and fluorocarbon leader lines will have less durability due to material differences and the purpose of it being a leader line. These will need to be changed out when you observe and feel fray on the line.  Braided fishing lines that are usually utilized for backing tend to have a longer life. However, the same conditions apply. All fishing line’s durability is dependent on wear and tear.The more you fish it, the faster it will break down. Always inspect for frays both visually and tangibly. Inspect all knots whether it is connected from your braided line to your leader line or your leader line to your hook as they are the weakest points between you and the fish. If you see fray near the top spool of your reel, cut them off and continue to use the line that does not have fray. Also pay attention to your spool. Once you have removed enough lines and do not have enough line capacity, it is time to respool and change your line.