; and (2) any reference in section 631(a) or 632(a) of this title to an officer who has failed of selection for promotion to the next higher grade for the second time shall be deemed to refer instead to an officer described in subsection (a) who has failed of selection for promotion to the next higher grade for the maximum number of times specified for opportunities for promotion to such grade within the competitive category concerned pursuant to such section 649d. 649g. Retirement: retirement for years of service