DWR Scalabilty And Early Closing Mode

We have a project that will run on a Websphere 6.1 server that needs to send data to the web client in real or near real time.  The data will be read from a JMS topic. We are considering using DWR "Reverse AJAX" to help push this data from the web server to the web client.  There are some concerns about how this would scale as well as failover.  There is also a concern about the "push" vs. "pull" concept.  

I read some about Early Closing Mode in DWR.  If I understood this correctly, DWR will close the http connection after 60 seconds if there is no activity.  A question I have is does it release the socket or thread once that connection is closed?   Would this approach be able to scale to thousands of clients or would a dedicated server component like Tibco "Ajax Messaging Service" which uses LightStreamer be needed in order to handle large numbers of clients?  The disadvantage I read about Early Closing Mode is that many clients may possibly try to re-connect at the same time.  How big of an issue is this?

Any ideas on this would be greatly appreciated.

Thanks
r123