Creating the Electronic circuits is Ok not so much complicated for experts. But needs to think about the persistence of the electronic circuits. Its very difficult to make the circuits to work for life time. But its important to have the long run electronic circuits.
Of course it depends on individual components that we assemble on the PCB. And are there any factors that need to be keep in mind while choosing and assembling the components to have high durability.
Best Answer
Don't use anything mechanical if you can avoid it - use solid state (like SSR's instead of mechanical relays, capacitive sensing/force sensing instead of switches, etc).
Use protection for every possible contingency - if it gets struck by lightning it needs to keep working.
Don't require any active cooling - fans break or get dirty too easily.
If it's in any kind of high-vibration environment, don't use connectors. Solder everything to the board.
If necessary, use redundant modules. I believe one of the Voyager probes has five independent computers any three of which are on at a time. They all work on the same problem and the solution that at least two of them agree on is used. The computer that created the bad solution is turned off and another is turned on in its place.
Have the ability to update any software on the device in the field when you find errors.