Hello,
For offline non-persistent VDI clients over time, obsolete clients can accumulate in the Symantec Endpoint Protection Manager database. Obsolete clients are those clients that have not connected to Symantec Endpoint Protection Manager for 30 days. Symantec Endpoint Protection Manager purges obsolete clients every 30 days by default.
If you do not want to wait the same number of days to purge obsolete non-persistent clients, you can configure a separate interval for them. If you do not configure a separate interval, then offline non-persistent VDI clients are purged at the same interval that non-virtual obsolete clients are purged.
Note: Online non-persistent clients count toward the number of deployed licenses; offline non-persistent clients do not.
Check these Articles:
Configuring a separate purge interval for offline non-persistent VDI clients
http://www.symantec.com/docs/HOWTO81115
Using Symantec Endpoint Protection in non-persistent virtual desktop infrastructures
http://www.symantec.com/docs/HOWTO81133
Symantec Endpoint Protection 12.1 - Non-persistent Virtualization Best Practices
http://www.symantec.com/docs/TECH191897
Hope that helps!!