So they should be ok for quite a while into the new century. There is some provision to carry 'spares' but for the most part we have a lot of redundancy built in to preclude it. That's pretty much what I do. Since I work software, my job 'touches' all of the other systems. So I end up 'taking care of' the unexpected in test.
Safety is our top priority, first to personnel then to flight hardware.
I apologise, Chips that do not recognise the year 2000. We should be unaffected by that. All of our doftware code has been built in the last two years, the firmware a little older than that but not significantly. SEUs, or single event upsets are a big concern for the electronics.especially the top tier computers that handle the safing operations. We have a 'scrub' algorithm that checks and corrects for single bit errors at 1Hz.