Sorry for the delay.
Once a worker thread is created, it will be reused. In particular, once it completes an invocation, it will sit in a read() waiting for the next invocation. If you do no more than one invocation at a time, the same worker thread should handle all of them.
If you do more than one invocation at a time, you could limit the number of worker threads to one. That way, if an invocation comes in while the single worker thread is busy, the server will wait until the worker thread finishes processing its invocation and then use it for the new invocation. You can limit the number of worker threads in the configuration file $JBOSS_HOME/server/$CONFIG/deploy/ejb3-connectors-jboss-beans.xml by changing the line