A damaged wiper blade cannot be expected to give good service. When you begin to see blemishes in your field of vision, it's time to change the blade.

A windshield wiper has no protective cover, of course. Even when not in use, it sits in its receptacle between the windshield and the hood subjected to the wind, rain and sun, 24 hours of every day, 365 days of every year.

A wiper blade begins deteriorating the very minute it's installed to the vehicle.