More of a comment, but a bit longer:
The sampling interval correlates with the time constant of the controlled system. You would need to find a system that is slow enough such that MPC with sampling time of a few months is still sufficient. Maybe you can control the movement of a glacier..
The chemical industry has some of the slowest controlled processes as far as I know (please correct me if there are slower controlled processes) which is also why it was the origin of MPC. Of course the time constant of the system is only an upper bound for the sampling time, whoever designs the controller might still decide to pick a shorter sampling time.