I wish I had a better answer to this, but our answer is “we don’t” 
We’ll add new features from the box in the top right of the editor, but we haven’t upgraded our Bubble engine in years due to worries of breaking changes in a complex app.
It would definitely be great if we could test the upgrade extensively on a “QA instance” before committing to the upgrade. Especially since it seems that you only have a set amount of time to revert the upgrade if something breaks.
2 Likes