If the truth be told, it is not usually absolutely necessary to clear preferences after every update. If it does need to be done, it is normally only after upgrading a major version (i.e., v5.x to v6.x). The reason I suggest to do it on the after-install welcome splash page is twofold: (1) It may be required with that particular upgrade, and (2) It doesn't hurt to do it anyway.
Since FEBE has been translated into over 30 languages, it isn't really practical to change the text on the welcome page after every update.
Of course, you could always use OPIE
to import/export the FEBE preferences