Seam - understanding PAGE scope and CONVERSATION scope

Question

I still get confused about the PAGE and the CONVERSATION (temp) scope. Maybe I get some help here. As fas as I know, variables outjected to the PAGE scope live as long as the user only postbacks the same page. The temporary CONVERSATION scope instead even survives a redirect to the next page. Here is a little example with two effects that are confusing to me:

First, component and outjections are in CONVERSATION scope and the tempUser data is displayed in a jsf page. But in the save method called from that jsf-page, the injected tempUser is null. Why?

Second, if I do the same but change component and @In/@Outs scopes to PAGE scope, the tempUser gets correctly injected on postback - but gets not saved, for wathever reason, although even the super.update()-method on userHome gets called. Or is there a problem in using the homeEntities that ways (the idea iwa to use them only as DAO wrapper)?

@Name("userAction")
@Scope(ScopeType.CONVERSATION)
public class UserAction implements Serializable {

    private static final long serialVersionUID = -4852371546895918692L; 

    @In(create = true)
    private UserHome userHome;

    @Out(scope = ScopeType.CONVERSATION)    
    @In(required = false,scope = ScopeType.CONVERSATION)
    User tempUser;

    @RequestParameter
    private Long userId;

    @Factory("tempUser")        
    public User getUser() {                     
        if (tempUser == null) {
            userHome.setUserId(userId);
            tempUser = userHome.getInstance();
            userHome.clearInstance();
        }
        return tempUser;        
    }

    public void save() {    
        userHome.setInstance(tempUser);     
        userHome.update();
    }
}

The xhtml contains a a:form with

<a:commandButton
  id="update"
  styleClass="button admin" 
  action="#{userAction.save}" 
  value="#{messages['user.action.update']}"/>

Thanks for replies. Sorry, if this is two problems in one.