I've found them useful in the stretch drive for a Cultural victory, when picking off Broadway, Rock'n'Roll, Hollywood, and the Eiffel Tower can give you such a big boost. But that's if you get them late in the game; Versailles and the Forbidden Palace are mid-game ploys. (I haven't had opportunity to use them in the way you suggest; a lot depends on getting the Pyramids, and that one eludes me much of the time.)