I think this is the enterprise parameter you're looking for:
Connection Monitor Duration: This parameter specifies the a common link qualifying time period for all the devices using a specific SRST reference.
This is a required field.
Default: 120
Minimum: 0
Maximum: 2592000
: Restart all services for the parameter change to take effect.
In later versions of CUCM this is also a Device Pool configuration.
hth,
nick