To ensure a smooth upgrade it would make sense to set an auto default upgrade window when no upgrade window was defined by the admin for a specific tenant.
It will be a safety net that upgrades will be run most likely in the non-working hours when it was missed to set an upgrade window
Ideas Administrator

Thank you for this suggestion! All environments now have default update windows set outside of regular business hours for the environment's localization country.

Best regards,
Joost Bulsink, Program Manager
Dynamics 365 Business Central