To be clear, the coolant system runs continuously, but the power draw of the machine is far lower when not being actively used.

why do they have to run continuously? I would expect the opposite to be true. It would have some cool-off periods etc.

MRIs use superconducting coils which can never be shutdown except in emergencies. There's a "quench" button which if you press the magnet turns off. But then I can't remember how much it is to turn back on but it's not a simple visit from a mechanic.

Considering they’re superconductors cooled by liquid helium there’s not a lot of scope for “cool-off” lol