There is a known issue in which daily maintenance schedules set for 24 hours cause some alarms to slip through. People often use this option to avoid calculating the number of hours and minutes the maintenance window should stay active. I propose a change to the GUI so that Once only allows a user to select a start date/time (current practice) and an end date/time rather than a duration. The back-end could then convert this into hours and minutes automatically. This would make it more likely that users would stop using Daily/Weekly/Monthly for long maintenance schedules.