That depends on a whole lot of factors....you are correct that the remote wipe commands do use push notifications. I have had both mobile devices and Macs off network take upwards of a few minutes to a few hours to "get the message". If the user isn't connected to a network, you can push until you are blue in the face and nothing will happen...when you reconnect to a network then, I have sometimes seen it take a few minutes. I've also noticed that sometimes a device will have a feedback token or show up as "busy" in it's listing of commands being run.
Push notifications are never perfect and I usually see sending a push as needing a window of time to complete if going to a large group of devices.
