JSF state saving on server

[Teena George]

Hello,

I was going through the book JSF in Action (Kito D Mann) By Manning publications. There is a statement
'If your JSF application saves its state on the server, there is no way for it to know that a view has expired.' Why is it so? The session timeout interval is configured in web.xml and is there in the server.
So I think the server can understand whether a view has expired or not.
Could anyone explain this, please?

Thanks,
Teena

[Teena George]

Does anyone have a clue?