The relationship between structural and functional brain connectivity across the mammalian lifespan is largely unknown. To elucidate the temporal characteristics of this relationship we longitudinally acquired high-field resting-state fMRI and diffusion-MRI in rats, from early infancy to old age. We specifically examined the interhemispheric connectivity between homologous primary somatosensory cortices, a major part of the sensorimotor system. The structure-function correlation increased from about 0 during infancy to 0.4 around adulthood, followed by a further gradual increase towards old age. This reflects dynamic patterns of lifelong brain remodeling, which may underlie variations in brain disease etiology during development and ageing.