I have had my car for 3 years and only just yesterday replaced my windwhield wipers. Most experts say you should change your wipers every year. In California that has seemed to me to be a little much since they don't get much use.
However, lately I have had plenty of use for it and have noticed my wipers not performing up to par so I replaced them. Makes a huge difference. Sometimes you just don't really notice because the detoriation is gradual but boy do they work a lot better now. What is with all this rain we are having. I really don't mind a little bit of rain but this is bordering on crazy. I moved back to California in part because the weather is better. Not lately it isn't.