Hi George,
I thought that there must be some way to change this but I guess not. I have searched every document that references CME Night Service and it seems that the 12 seconds is a pre-defined (non changeable parameter)
The night-service feature allows you to provide coverage for unstaffed extensions during hours that you designate as "night-service" hours. During the night-service hours, calls to the designated extensions (known as night-service directory numbers or night-service lines) send a special "burst" ring to phones that have been specified to receive this special ring (the phones are known as night-service phones). Phone users at the night-service phones can then use the call-pickup feature to answer the incoming calls from the night-service directory numbers.
For example, the night-service feature can allow an employee working after hours to intercept and answer calls that are presented to an unattended receptionist's phone. This feature is useful for sites at which all incoming public switched telephone network (PSTN) calls have to be transferred by a receptionist because the PSTN connection to the Cisco Unified CME system does not support Direct Inward Dialing (DID). When a call arrives at the unattended receptionist's phone during hours that are specified as night service, a ring burst notifies a specified set of phones of the incoming call. A phone user at any of the night-service phones can intercept the call using the call-pickup feature. Night-service call notification is sent every 12 seconds until the call is either answered or aborted.
From this doc;
http://www.cisco.com/en/US/products/sw/voicesw/ps4625/products_configuration_guide_chapter09186a00807dc29a.html#wp1097582
Sorry, I know this isn't the answer you were looking for!
Rob
