A maintenance window should suppress the alerts a planned change causes, and nothing else. Here's how to scope one correctly.
Create the window under Alerts > Maintenance and select only the devices and links actually affected by the change, not the whole site; an overly broad window hides real problems on unrelated equipment.
Add a 10 to 15 minute buffer before and after the planned change window to absorb reboot time and route reconvergence, so the alert doesn't fire the moment the window closes.
Maintenance windows close automatically at their scheduled end time; there's no need to remember to turn one back off, but it's worth confirming the end time is correct before you start.