How to determine the expected return period of patent

Hello! Your question is contradictory. 1. The protection period (legal life), transfer right, license right (contract life) and technology life cycle (technology life) are consistent according to law, at least! There are no years 18, 15 and 12. And there are benefits after the expiration of the protection period (technology can continue to be used and sold, etc.). )! 2. Answer: The expected return period is longer than the guarantee period (18 years).