Before revision:  Accurate simulation of the mean age of DCVs in boutons requires the development of a model that would account for both residentand transiting populationsof DCVs . In this paper, such a model is developed.
After revision:  Accurate simulation of the mean age of DCVs in boutons requires the development of a model that would account for resident, transiting-anterograde, and transiting-retrograde DCV populations . In this paper, such a model is developed.