To my understanding, the time limit of fission is mostly due to political/security reasons. Of course keeping it indefinitely on will require huge maintenance

To my understanding, the time limit of fission is mostly due to political/security reasons. Of course keeping it indefinitely on will require huge maintenance costs but if the infrastructure is modular enough to be able to replace every elements, that may be doable. With fission the structure of the building is part of the infrastructure’s security so it’s harder to change when it’s too damaged. Maybe I’m wrong but it seems like fusion doesn’t require huge cement walls that would take a lot of constraint and which would effectively limit the maximum lifetime of the building.