Automatic deleting of registry keys from the virtual store

I thought I read an article, which stated that registry keys would be automatically deleted from the virtual store, when users either log off or log on using vista. I tested this for standard users and for users with admin privileges. The registry keys in the virtual store were not deleted. I tried to find the article but I could not find it. Maybe I just mis-understood what the writer stated. Does anyone know if the registry keys for the virtual store should automatically be deleted? Thank You!