Authentication tickets expire after set time, but would be more useful to have them expire after an inactivity timeout.

Currently, tickets expire based on authentication-services-context.xml:

<!-- The period for which tickets are valid in XML duration format. -->
<!-- The default is P1H for one hour. -->
<property name="validDuration">
<value>P1H</value>
</property>
<!-- Do tickets expire or live for ever? -->
<property name="ticketsExpire">
<value>false</value>
</property>

It would be more useful to have tickets expire after a user-definable inactivity timeout.