As I said it's only for expiry date and some business to make money , global business, maybe something happened if you don't change rear deff on time, who knows, but there is a reason to void warranty, there is some expiry date on the parts, but always they keeps themselves on safe side, opposite the costumers is right at end blaming them, they have average service data on the cars, so they make time tables for service, expiry date is mandatory even for the salt they procedure from one million years mine, selling with 2 years expiry date 🙄