By default, the VPN On Demand has an idle timeout value of 120 seconds. However, when a VPN is launched using Pulse Secure Mobile Client the idle timeout value and the session timeout values are determined by the roles that are assigned to the users.
For more information, refer to http://help.apple.com/configurator/mac/2.0/#/apd4CE9487D-EC56-4548-BE53-12639EAF8CACExcerpt:
"The device closes a VPN session initiated by VPN On Demand after two minutes of inactivity. If the connection was initiated manually using the Settings app, the VPN server’s timeout applies."