
If you aren't yet at 300 coins (for Gold) or 600 coins (for Platinum), and you've got more games to register, get to it right now! If you've been thinking of picking up Punch-Out!! or something this week, you should probably do it today! Conversely, if you're at 600 now and you have more stuff to register, wait until tomorrow so it counts toward next year's total!
If you're not sure about the eligibility of an older (pre-Club Nintendo) game and don't want to waste time registering it, consult the list of eligible games in the "Product Registration" area of the Club Nintendo FAQ.

