I think it is unreasonable to expect networked software to stay secure for that long. If it isn't networked in any way then sure, that might work but then again, 30 years is a long time.
Adding remote software control to physical things like water treatment and electrical systems adds a lot of convenience, safety, and saves loads of money but perhaps some of that savings should be spent on more vigilance in regards to security.
Adding remote software control to physical things like water treatment and electrical systems adds a lot of convenience, safety, and saves loads of money but perhaps some of that savings should be spent on more vigilance in regards to security.