The disagreement between evolutionary and dynamical time scales for the evolution of the central stars of planetary nebulae (CSPN) through the H-R diagram is investigated. Three possible reasons for the disagreement are examined: (1) the nebulae could have experienced a phase of rapid photoionization of material ejected previously while the stars were still on the AGB; (2) the central stars could have undergone a late helium shell flash and returned to the AGB; and (3) the AGB-CSPN evolutionary transition times could have been increased by small additional amounts of residual envelope material remaining after the superwind mass-loss phase. Mechanism (3) is favored here because it can account for evolutionary ages both less than and greater than the corresponding dynamical ages.