I thought about this too a Free DLC upgrade that could be removed after the 'special' period is over. You say they're entitled to re-download the DLC if needed, but does that still count even when the DLC option is later removed from the app? An issue I'm concerned about is piracy if the 'Limited Edition' with the free DLC button is leaked to pirate sites, does that mean pirates will all be constantly downloading the DLC for free, or can the DLC be removed through iTunesconnect?