You can also very easily keep the game archive you downloaded, since there's usually no DRM to prevent it. And sure, that's not always possible, but for a game you downloaded for free during a promotion? If you lost the download and want it again, no offense, but maybe you should consider buying the game if you like it so much. That way you'll own it in perpetuity and you'll be able to download it again any time you want from any computer.