You're right to be cautious. Microsoft 365 does require the device to connect to the internet about every 30 days to keep the license active. If it doesn't, Office apps go into reduced functionality mode (basically read-only).

Unfortunately, Microsoft doesn’t expose the actual license validation date or the number of days remaining in any way that's accessible via VBA or even PowerShell. It's all managed internally by the Click-to-Run service, and there’s no registry key or public API that provides a countdown.

That said, you can work around it by using VBA to log the last time the machine was online. On workbook open, check for an internet connection. If it's online, write the current date to a local text file or a hidden worksheet. Each time the workbook opens, compare today's date to that last online date. If you're getting close to 30 days, display a warning message.

You can probably find example scripts online that do this, or write a simple one yourself. It’s not too complex.