It would have been nice to have had these during my first playthrough. Fortunately, the game is good enough for me to want to play through it several times, so it's ok. If you haven't started the game yet, make sure that you input the code for "Special Event 3" at the beginning since it unlocks a few extra storyline threads for Gemini. The others look like they can be inputted at any time without impacting the story.