My 99 DOHC Taurus has 62000 miles but I don't know if the serpentine belt had been yet replaced by the previous owner. How should I decide if it needs to be replaced? Right now, I see no cracks or scratches on it. In some places, there are barely visible perpendicular stripes, but I am not sure if those are scratches or just a feature of the belt. There is no noise coming or any known issues right now.