Because I'm about to fly LY which (apart from its own FF program where the miles expire three years after earning) you can only credit to either QF or SA frequent flyer programs and I wanted took figure out which to use. SA seemed best since it can also collect B6 flights but then I discovered thanks to your and others expertise that SA miles are useless and I won't be able to keep them valid for long enough to be able to do anything with them before they expire.