As per New Zealand Thoroughbred Racing

•A name cannot be reused until 15 years has elapsed since the foaling of a similar named horse.
•Names for broodmares cannot be used again until 12 years has elapsed since that name last appeared in a Volume of the Stud Book.
•Names of winners of Group One races are protected.
•Name of a Stallion cannot be used until 15 years after it last appeared in a studbook.