When a client invokes the create method on an statefull
EJB home, it�s life cicle begins, the container than invokes newInstance() on the bean class, creating a new instance of it,then the container invokes setSessionContext and finally ejbCreate once the ejbCreate has finished the container than returns the ejb remote reference to the client.
About swap I think that it can be implemented and also some kind of pool using cache memory but that�s a vendor specific implementation, but one thing I think most vendors do is passivating the bean when the bean instance is not servicing methods from the client to preserve resources.