[Zope] CoreSessionTracking timeout

Hi, I am playing around with this great product and (nearly) all works as expected. This is exactly what I need for my application and you guys are saving a lot of time for me! Thank you. The only thing I don't understand is the timeout of session_data_manager. If I test the example given in the help I expect 'Before change:' to be empty if called the first time (works) and filled for each subsequent call (works also). If timeout expires I expect 'Before change:' to be empty again, thus generating a new token. But it isn't. It still uses the old token. What's going on? I tested with cookies and form vars namespace, but it has always the same behaviour. What's the quirk? Oliver