If you don't need the result and you own the Web Service you should consider implementing the fire and forget functionality on the web service side through the SoapDocumentMethodAttribute by setting it's OneWay property to true.
When an XML Web service method has the OneWay property set to true, the XML Web service client does not have to wait for the Web server to finish processing the XML Web service method. As soon as the Web server has deserialized the SoapServerMessage, but before invoking the XML Web service method, the server returns an HTTP 202 status code. A HTTP 202 status code indicates to the client that the Web server has started processing the message.
João Angelo
2010-09-16 15:34:15