How would you setup an JSF entity, service and backing bean

Question

I would like to ask expert opinion regarding the correct use of entities, service and views. It's regarding best practices, so I hope my question doesn't get flagged as too vague.

So I have the following components in my app (only regarding the session):

//database table that holds current session info    
@Entity
@Table(name="oauth2_customer_session")
public class OAuth2CustomerSession implements Serializable {
   //get/set properties
   ...
}

//the service that retrieves and updates OAuth2CustomerSession entity
@Stateless
public class SessionService {
   @PersistenceContext(unitName = "acme-db")
   private EntityManager entityManager;
   ...
}

//the backing bean
@Named("customerSession")
@SessionScoped
public class CustomerSessionBean implements Serializable {
    @EJB
    private SessionService sessionService;
    private OAuth2CustomerSession customerSession = null;
    private HttpSession session;

    public CustomerSessionBean() {
        session = (HttpSession) FacesContext.getCurrentInstance().getExternalContext().getSession(true);
    }

    @PostConstruct
    private void init() {
        sessionId = session.getId();
        //service will return a valid customerSession object
        customerSession = sessionService.findCustomerSession(sessionId);
    }
    ...
}

Right now, I'm passing the customerSession object as a parameter in a few of the sessionService methods.

I'm thinking this way, the sessionService remains stateless, thus reducing overhead? But would passing the customerSession object create too much overhead and/or violate the recommended guidelines?

thanks in advance!