Hi Christian,
This setting is also applied to all Incoming and Outgoing CUCM calls;
Clusterwide Parameters (Feature - General)
Maximum Call Duration Timer :
This parameter specifies the minutes that a call can remain active before Cisco CallManager clears it. A value of zero disables the timer.
This is a required field.
Default: 720.
Unit: min.
Minimum: 0.
Maximum: 35791.
Hope this helps!
Rob