Can we disable Tridion publishing during a maintenance window (for couple of hours)? Is this just a matter of removing Allowed Publications from the Publishing Targets section?
As Marko mentioned, if you want to suspend publishing altogether, you could just stop all Publisher Services.
If you are using Topology Manager, you can also mark individual CD Environments as "offline". This will suspend publishing to those CD Environments only.
Maybe a reason to migrate to Topology Manager based publishing? :-)