emergency data recovery
The most worst scenario will be if your second brain is running well and you operate on the PKM mastery, that some Windows/Libary update will distroy the access of all your ideas, thoughts and connections.
PB free versions should be able (also with old brains) to export all thoughts and especially also the links and attachements into a folder hierarchy with plain text files. So in this worsed scenario with a licenc free and without any software activation process it will be possible to see and search over your ideas, thoughts and connections with some third party tools, to continue working efficient like you know it. [If you leave Everynote, sure you can export all in plain text, but all your links get lost, so all your idea-space becomse meaningless]