Larman says (p. 22) that as the system goes through more iterations it converges “towards final requirements and design” and draws a wavy graph with the size of the waves diminishing with time. My experience seems to disagree with that. As long as the system is “alive” there is no such thing as ‘final requirements’: new features and requests are invented all the time. Occasionally they are just incremental, but frequently they change significant portions of existing functionality.