On Android I have seen a few apps that say that one should make sure the app is the same version as the app that made the backup. In other cases, far more cases, the backup version changes in ways that the new app can’t handle older backups.
So how resilient to data rot is .JEX?
It’s a good question. Currently the JEX format is not versioned but for example an old JEX file should work in new versions of Joplin, and missing properties will simply be set to a default value.
This has not been tested yet though.
One reason there’s few tests for this is because the JEX format is quite simple, so let’s say you find and old JEX archive that no longer works with new version of Joplin. In that case you’re aren’t stuck with an unreadable file. You can open it yourself (it’s a tar file), extract the Markdown files, read the notes, etc. Basically nothing is lost.
If such situation happens however, most likely I will (or someone will) fix Joplin so that it can import that old JEX file.
Excellent. That is good enough for me.