The destroy attribute of FilterConnection will be set to true when the client decides to destroy a persisted filter before all of its applicable messages have been pulled. If and when the client does pull all of the persisted filter's applicable messages, then the web service will automatically destroy the connection and return an empty pull response. If the client does not pull all of a persisted filter's applicable messages and does not explicitly destroy the persisted filter by setting the destroy attribute to true, then based on an agreed upon out-of-band policy, the web service will expire the persisted filter after X number of days.