Check your Amazon affiliate links regularly
Amazon has a habit of moving/removing/changing some products. and I found out the hard way. I looked at a product I have on my site and noticed that not only the price had changed, it was no longer available for free shipping for Prime members -- and I had touted the price and free shipping on my site! I don't think anyone was inconvenienced by this since I seem to be the only visitor to my site :(
Anyway, I'm going through all my Amazon links and changing/updating the links if the pricing or anything else has changed since I featured the product on my site. You may want to check yours on occasion too.