You can control the hours of the day during which you want (or don't want) review requests to be sent. By setting send hours, you can ensure contacts don't receive review requests or reminders automatically during certain hours, for example late at night.
To update your send hours, click to the Campaigns section of your dashboard. Go to #2 - General Settings, and click anywhere to edit:
Then, in the Schedule Settings section, you can change the time during which campaigns are allowed to send, using the Allow campaigns/reminders to send between setting:
Make sure to hit "Publish" at the top to make any campaigns changes live for future review requests!