You would only need to schedule downtime if you are deploying a new version of an Integration Pack that is already installed as the Deployment Manager will first attempt to uninstall the existing version before installing the new version and the uninstall
would fail if the binaries are in use. Deploying without stopping the runbooks would result in file removals and replacements being scheduled to occur during the next reboot so that files in use could remain in use to complete whatever they are doing
etc.
Regards,
Jeff.