Children of women inmates may only participate in the program until they reach the age of six years, at which time the Board of Prison Terms may arrange for their care elsewhere under any procedure authorized by statute and transfer the mother to another placement under the jurisdiction of the Department of Corrections if necessary; and provided further, that at its discretion in exceptional cases, including, but not limited to cases where the mother’s period of incarceration is extended, the board may retain such child and mother for a longer period of time.