Satoshi's answer for this was that there should only be one implementation of the full node software. He should have talked to a release engineer. There are al

Satoshi's answer for this was that there should only be one implementation of the full node software. He should have talked to a release engineer. There are always at least two implementations of a piece of software: the stable version, and the prerelease version. With Herculean effort and focus one could theoretically arrange a system where every customer on Earth runs version N until midnight on Dec 31 and runs version N+1 one microsecond later. You would have to distribute the new code in advance. But it wouldn't ever be perfect, because networks get partitioned: someone's PC would be unplugged when the patch was pushed. And what's the rollback procedure when you push the unforeseen bug?