The specific life expectancy of Gallimimus is not well-documented, as it can be challenging to determine from the fossil record. However, like many dinosaurs, it likely had a lifespan that spanned several years. Comparable theropod dinosaurs, which Gallimimus belonged to, often had lifespans ranging from 10 to 30 years or more, depending on factors such as growth rates, environmental conditions, and predation pressures.