We advise to replace them if they are: chattering, streaking, smearing, squealing, or outright broken. If yours last a full year, great! It is pretty easy to tell if your blades need replacing, you’ll see it (or not see anything) right in front of your face! A lot of places will tell you that you need to replace wiper blades every 6 months. Keep in mind, Wiper blades of vehicles that live on the street and are exposed to the sun or other conditions daily, will not last as long as a garaged vehicle . We recommend, you should always have your repair shop check your blades when you go in for an oil change.