does not make sense.
With subtree_expiry you set in which part of tree published objects will trigger cache expiry.
Also $uri_string and $current_node.node_id carry same information so you don't need it both. This will do want you want:
The thing is that the menu items are editable, so when I change the title of menu item 1 to menu item 2, the pagelayout should be invalidated. This behaviour should be the same for submenu items.
Yes. If you don't place subtree_expiry that cache block will expire after publishing objects anywhere in the tree. Here is more about this: http://ez.no/doc/ez_publish/technical_manual/4_0/reference/template_functions/miscellaneous/cache_block
