Our prior work developed CO2-Bulk Energy Storage (CO2-BES), which uses geothermal power plants and sedimentary basin geothermal resources to time-shift electricity production. In this study, we investigate the maximum duration over which CO2-BES can time-shift electricity generation because there is increasing evidence that, in addition to shorter-duration energy storage approaches, like batteries, energy storage approaches capable of time-shifting electricity generation over long-durations (>10 hours) or even over seasons will be needed in future decarbonized electricity systems. We use an integrated model that we developed and characterized with specific facility-level assumptions to simulate CO2-BES operation and find that a CO2-BES facility operating under these specific assumptions can time shift electricity over durations of at least one week and likely multiple weeks. Time-shifting electricity generation over longer durations (e.g., one month) depletes subsurface overpressure enough that brine flashes in the production well, but durations longer than a couple weeks are likely possible with different facility-level assumptions. Towards this possibility, we conclude with a few ideas for future work that could enable seasonal energy storage with CO2-BES. Overall, this study suggests that CO2-BES specifically, and sedimentary basin geothermal resources generally, can provide long-duration energy storage and show promise for providing seasonal energy storage.