There is no defective knife or a knife that does not have to get sharpened. Sharpening is a part of the life cycle of a knife, like taking a shower every other morning is for us. Even ceramic blades need to be tuned from time to time to ensure proper cutting. While not as popular, ceramic knives are known for withholding a sharp bevel longer than traditional metal knives. Be aware that when shopping for ceramic knives, you may have difficulty finding a sharpening service that can set them up correctly when they need to be sharpened. You can read more about Knife Bevels
in the article.