To modify the Antivirus and Antispyware policy's notification settings:
1.Log into the SEPM console and select the Policies tab
2.Select the Antivirus and Antispyware Policies link from the View Policies pane
3.Select the policy used by the affected clients from the Antivirus and Antispyware Policies pane
4.Click the Edit the Policy link in the Tasks pane
5.Expand Windows Settings and select the Miscellaneous tab
6.Select the Notifications tab in the Miscellaneous pane
7.Set the Days before a warning appears in Symantec Endpoint Protection value to the number of days calculated as "safe" for the affected clients.
8.Click the OK button to close the AV Policy window and save the changes to the policy
http://www.symantec.com/docs/TECH150078