The AutoZone lifetime warranty is a warranty that last for the part you buy for as long as you own the vehicle yourself.
But when you sell or trade in the vehicle then the AutoZone lifetime warranty on the part expires and is no longer valid to the new owner of the vehicle.
But as long as you own the vehicle and have the receipts and paperwork with you on the lifetime warranty then the AutoZone lifetime warranty on the part will be effective for as long as you own the car or vehicle.
But as soon as you sell or trade the vehicle or car to someone else then the AutoZone lifetime warranty is no longer valid.
If the part fails at anytime during the lifetime of your vehicle when you own the vehicle then AutoZone will replace the part without any charge.