I have an advertisement I would like to run between 1:30 AM and 4:00 AM the first rime it is available. I have created a maintenance window for those hours in the specific collection, the question is what happens if the client has other windows? Will my window be overridden?

The way I understand Maintenance Windows is that if a system belongs to multiple collections, and each collection has a different maintenance window defined, the system is subject to all of the maintenance windows. They do not cancel each other out.--Joe.