Sorry to hear it timed out during a demo for you.
The default timeout is 30 minutes, it can be configured (and disabled) in ncs.conf.
From ncs.conf(5) manual page
/ncs-config/webui/idle-timeout (xs:duration) [PT30M]
Maximum idle time before terminating a Web UI session. PT0M means no timeout. Default is PT30M, ie 30 minutes.
/ncs-config/webui/absolute-timeout (xs:duration) [PT16H]
Maximum absolute time before terminating a Web UI session. PT0M means no timeout. Default is PT16H, ie 16 hours.