How can a admin backup CAL's and server keys and re-use them on the same server? Or if we build a new one and transfer the keys to a new 2016 server? From what i have been able to read it seems that once the keys are in thats it, no going back. If the server fails and needs replaced you have to buy the keys again. I am hoping that I am missing something import and be able to link them to a login much like can be done on windows pro.
It all depends on what type of keys you have. If they are OEM then yes you would have to buy a new key if the server totally died. If they are part of an agreement with Microsoft then you have more options.
With your CAL's you only ever need to install RDS CAL's which can be migrated to another server if the original one dies.