Older designs are better for this. The tighter we push tolerances the sooner failures will happen. Since you haven’t set any performance requirements… if you a

Older designs are better for this. The tighter we push tolerances the sooner failures will happen. Since you haven’t set any performance requirements… if you are happy with using a RTOS instead of something like Linux, you could look at super basic parts, no electrolytes drying out in solid state capacitors. I’d be pretty confident a high end Arduino style Atmel/AVR based “computer” could be easily designed to last 20 years or even longer. Add some redundancy and dip switches or electronic fuses for failover to the replacement parts, as rare as such failures would be in older style designs. Because we understand so much more about how the underlying mechanisms work, out of necessity in order to develop more advanced designs, but understanding these things means we could also develop older style things more reliably.