There is no uniform legal definition of "lifetime warranty," according to Consumer Reports. Some states may have their own warranty rules. In California, for example, a lifetime warranty must state a duration or how it can be determined, reports the Hanford Sentinel.
A lifetime warranty for an automotive part can refer to the lifetime of the vehicle, states the Federal Trade Commission. However, a lifetime warranty may be valid for the lifetime of the original owner.
Another interpretation is that a lifetime warranty covers the expected lifetime of the product, explains Michael Dorf. This interpretation is somewhat uncommon because the expected lifetime of a product is unclear. Some courts have interpreted lifetime warranty to mean that whenever a product breaks, its lifetime is over at that point.