/SHUTDOWN[:n Waits for monitored applications to shutdown, shuts down VSPerfMon.exe, and then waits for the shutdown to complete. ...

/SHUTDOWN[:n]   Waits for monitored applications to shutdown, shuts down
                VSPerfMon.exe, and then waits for the shutdown to complete.

                If n is specified, VSPerfCmd will wait at most n seconds.
                If n is not specified, VSPerfCmd will wait indefinitely.
                This eases use of VSPerfCmd as part of a batch process.