Active Sending Window
You can change your active sending window in Text Messaging -> Settings. The Active Sending Window will allow you to set certain times of day to NOT send messages before or after, to be more respectful to your recipients.
When a text message is queued to send to a large number of recipients, it may take some time for all the individual messages to send. For example, if you schedule a message that will take 6 hours to send, and you schedule it to send at 6pm, the last messages won't reach their recipients until close to midnight. If you have your Send Window Close set to 9pm, then the schedule will pause and the remainder of the messages will begin sending at your Send Window Open time.