This object specifies the time in units
specified in csneFilterTimerUnit for which
the notification specified in snmpNotifyFilterSubtree
will remain active with the corresponding
snmpNotifyFilterProfileName.
If set to 0, it indicates that the corresponding
snmpNotifyFilterSubtree will remain active forever.
This value can be set when the snmpNotifyFilterRowStatus
is active. If this is done, the csneFilterOperTimer will
be refreshed to take the new value set in this object.