Looks like you can change it in CUCM 8.6 via CLI:
Here is the link to the actaul command:
HTH, please rate all useful posts!
This command is not working for CUCM 8.0.3, is this normal?.
Be aware that the new session timeout value becomes effective immediately for a new CLI session; however, active sessions retain their original timeout value. Also the show cli session timeout command reflects the new value, even if the current session does not use that value.
If you mean you cannot find it, most likely because it's not implemented in that version.