Abstract: Highly compacted bentonite is the preferred buffer/backfill material for deep geological disposal of high-level radioactive waste, where its long-term volumetric stability plays an important role in ensuring repository safety. This work provides a comprehensive review of the volumetric deformation mechanisms and time-dependent characteristics of highly compacted bentonite, with a focus on recent progress in microstructural aging due to resting time, creep behavior, and relevant constitutive modeling. Recent studies reveal that prolonged aging time induces microstructural homogenization, diminishing swelling capacity and altering time-dependent deformation. Creep behavior and strain rate effect driven by particle rearrangement, pore water migration, bond breakage, and adsorbed water viscosity are significantly influenced by temperature and suction. Creep models for highly compacted bentonite are mainly based on elasto-viscoplastic theory, with overstress formulations incorporating thermal and hydraulic effects to capture creep and rate-dependent behavior. However, current studies overlook the time-dependent nature of external loads such as chemical conditions, temperature, and suction, limiting their applicability under long-term repository environments. In particular, the long-term impact of saline groundwater infiltration on deformation behavior of bentonite lacks systematic investigation. Future research should target multi-scale creep responses under extended resting and complex CHT conditions to enhance predictive models and repository safety assessments.