I bet they either have to keep it operational or at least operational-ready for set amount of time. I used to work at a place that got subbed gov contracts for IC packaging and they are still using chips that were the backbone for stuff like paveway missile systems but we were converting from milspec hermetically sealed ceramic to cheaper commercial plastic packages. That company essentially bought one of the Raytheon lines because they did not want the expense of keeping it running. Another time they took over mfg from another sub that Motorola used for a gov contract. Even though we set up the mfg on our own machines, we had to take in all these older machines that the process was originally set up on 'just in case'. "Russians Uncle Sam dont take a dump, son, without a plan" indeed.
there are actually businesses where it's their job to store backup wafers/packages for military/ITAR chips hermetically sealed up 'just in case'. The gov contracts for ITAR stuff usually have very long (20 years) keep-ready clauses where mfgs are supposed to maintain the line/capability to mfg if needed.
It would be interesting to see it would ever come to "fuck your pentium, bro; we need 500,000 camera ICs for our soldier's HUDs made pronto"