Hi @Aaron Fracht-Monroe,
exclusiveDuration appears in the list of Request DTDs (Document Type Definitions), which define the login and logout messages your application can send to the
Cisco CallManager Extension Mobility Login Service.
Based on the examples on page 23 of this Cisco CallManager Extension Mobility API Developer’s Guide (<--- external link), it appears exclusiveDuration is used to specify a Time Restriction for the session duration. An unlimited option is also available:
<exclusiveDuration>
<indefinite/>
</exclusiveDuration>
Hope this helps!