Staggered Messages will go out within the specified time you have booked them for.
The messages will go out every minute until the campaign is sent out to all the contacts you have booked to. For example: Book a staggered campaign to 1,200 people for 2 hours and the messages are sent out to 10 contacts per minute.
Staggered Messages are set-up using the same Message booking process, however Select Staggered instead of Standard and choose the send time. You can use the LIMIT option if you would like the campaign to go to a lesser number of contacts than the list or group size is. For example, you can use a LIMIT of 800 for a group size of 1,500 and the campaign is sent out to just 800 randomly selected contacts. 