I just changed my windshield wipers for the first time since I got my car, which was almost 3 years ago. Is that dangerous? The packaging says they recommend changing the wipers every 6 months. It’s also recommended that you change your engine oil every 3,000 miles or 3 months. I shoot for about 5,000 miles. And thanks to Jerry for pointing this one out: you shampoo instructions say that you should lather, rinse, and guess what…REPEAT. Are these recommendations all there just to get us to spend more money or what?