Why not just override the default jndi name to a jndi name of your choice? That way you don't have to worry about the .ear file name. See this for details http://docs.jboss.org/ejb3/docs/tutorial/1.0.7/html/JNDI_Bindings.html
If I use explicit bindings I'll get namespace clashes if that EJB package is deployed more then once within the container.
I believe there is a jboss/vendor specific way to do this in JBoss 5.1, I saw it on another site but I didn't save it unfortunately.