There is no published release schedule for Symantec Endpoint Protection (SEP) non-antivirus signatures.
File-based AV - Updated daily (with SEP's Multiple Daily Definitions, certified content is typically released three times a day Monday through Friday; one time per day on weekends).
Network-Based Protection (IPS)- SEP Security Updates (SU) are generally updated on Weekdays (M-F - no releases scheduled for weekend or major holidays in the United States).
Behavior-Based Protection / Proactive Threat Protection - There is no set schedule. The article linked below contains additional information.
Reputation-Based Protection (Insight) - Continually updated as it is a cloud based detection.
For additional details please visit: http://www.symantec.com/security_response/definitions.jsp