Long-storage quantum memories (QM) are necessary devices for long-range quantum communication. 100 ms QM storage times are required for a continent-scale fibre network. Erbium-based QMs directly couple to telecom-wavelength optical fields, making them directly compatible with existing telecom infrastructure. Recent experimental efforts in an erbium material, ¹⁶⁷Er³⁺:Y₂ SiO₅ ,have demonstrated a telecom-wavelength, highly efficient and multimodal QM based on the Rephased Amplified Spontaneous Emission (RASE) protocol. The memory storage time, however, was only tens of microseconds due to dephasing on the hyperfine transition. In this work, storage times of over a second were achieved by applying radiofrequency (RF) hyperfine rephasing pulses. The RF circuits and pulses were carefully designed to maintain high memory efficiency by achieving >90% hyperfine rephasing efficiency. Optical spectral diffusion due to host spin dynamics were measured and modelled to show that the memory multimode capacity is dependent on the storage time, but the trade-off is only significant for storage times of ≥O(100) seconds.