Well, it hasn't been below 350K more than once in the last 12 months. It has now gone 3 months in a row with 400K +, but I believe Rol is right, and that it will fall off in post christmas.
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS







