Hi Andy, thanks for your question. Our recommendation on the lifespan is anything 10 years or older should not be used. We recommend replacement at 10 years, due to deterioration of the plastics used in construction of modern restraints. A seat may have become brittle over time, and simply will not provide the same level of protection against impact. Older child restraints may not contain all the safety features of the latest Australian Standard. Kind regards, The Britax Team.