Currently, we can't implement more than one maintenance window for a resource.
Two suggestions here, allow us to assign multiple maintenance windows to a resource, or extend the "Schedule Frequency" functionality within the maintenance window editing screen to allow multiple start and end times.
This enables us to schedule maintenance windows for as many scenarios as we'd like. A few examples in point, we have multiple customers with a load of VM's who go through patching cycles, daily power downs and weekend power downs, all of which generate hundreds of alerts that could be stopped if the above functionality was introduced. Currently, we can only choose one of these events to stop alerts for.
An important change to reduce junk alerts, at least for us; when you have 320+ resources being monitored and 10,000 CloudMonix alert emails since the beginning of February ;)
I support Sam here with expansion of the maintenance windows. As we manage services on behalf of Customers, there are maintenance windows that get approved through change management and these might have 1 or more start and end times. It is important that we are able to get the alerts that allows us to manage the services correctly for the Customer and at the same time, minimise the amount of admin that might be created due to "false-positive" alerting when maintenance is being performed.