An important aspect of Family Language Policy in bilingual families is parental language choice. Little is known about the continuity in parental language choice and the factors affecting it. This longitudinal study explores maternal language choice over time. Thirty-one bilingual mothers provided reports of what language(s) they spoke with their children. Mother-child interactions were videotaped when children were pre-verbal (5M), producing words in two languages (20M), and fluent speakers (53M). All children had heard two languages from birth in the home. Most mothers reported addressing children in the same single language. Observational data confirmed mothers' use of mainly a single language in interactions with their children, but also showed the occasional use of the other language in over half the sample when children were 20 months. Once children were 53 months mothers again used only the same language they reported speaking to children. These findings reveal a possible effect of children's overall level of language development and demonstrate the difficulty of adhering to a strict "one person, one language" policy. The fact that there was longitudinal continuity in the language most mothers mainly spoke with children provided children with cumulative language input learning opportunities.