According to the bambulab blog (on the official bambulab website) they explicitly state that you are free to downgrade or not upgrade and your printer will still work.
Edit: they even have a specific note about users that never want to upgrade and it states that it is fine, and their printers will still function.
Rossman pointed out that they said they’re going to stop you from printing if you don’t upgrade the firmware. Maybe a timeout built in?
According to the bambulab blog (on the official bambulab website) they explicitly state that you are free to downgrade or not upgrade and your printer will still work.
Edit: they even have a specific note about users that never want to upgrade and it states that it is fine, and their printers will still function.