The best way to answer your question is to specifically read the manufacturer's warranty given for a particular product. As a general rule and part of the custom and practice in the manufacturing industry, a product's warranty should begin running when the product is purchased by the consumer not when the product is made.If the item sits in the box for a year at the manufacturing plant and the item turns out to be defective when used by the consumer, the consumer should not be held to having to keep a defective product that was not even used.