If it's about to fail, have a replacement ready.
And, probably, they could run their software under an emulator, on any US$200 desktop PC.
Indeed. The major annoyance I see is the radios interfering with each other. The centralized control architecture is also something I'd like to change. Each building does not require anything much smarter than an Arduino to be completely standalone and, if you want to be fancy, an RPi to send collected data to a centralized location.
I suggested a US$ 200 PC because many of those have no moving parts and more storage space than any Amiga ever dreamed of. They should be able to easily last 30 years or more.