I think in maintenance we should execute company instructions. but in common instruction we have :
1- check lose connection at a time-schedule
2- use protection circuit for any part for example use snubber or free-wheel circuit , correct breakers ,....
3- replace timeworn parts according to instructions.
4- clean all device (dust, trash particles ...)
...
Copy the soft ware onto some long lasting media (not Zip cassettes) and store them some where safe along with any loading/running instructions so anyone not familiar with the system can restart it from cold.
Out in the real world industrial computers run until the plant is replaced. For instance there are systems I worked on in 1989 which are still running and the software is backed up on 3 1/4" floppy discs. how many PCs can run these?, make sure you keep a machine.
Frank