No there isn't a place to change the time for email notification. Emails are sent when an alarm occurs that matches the categories and the severity levels you select. - http://www.cisco.com/c/en/us/td/docs/net_mgmt/prime/infrastructure/3-0/administrator/guide/PIAdminBook/config_server_settings.html#63370
I would work with TAC to see what the issue is, I don't believe Prime is at fault for the delay but I don't know your network.