Something I've noticed is that no one releases big games on the week of Obon or Golden week. Why is that? Wouldn't releasing it during those week rather than before those weeks produce more sales potential?
By releasing during holiday week itself you run the risk of mixing launch sales with holiday boost sales and losing a bit of both in the process - either from retailers ordering too few copies, and the holiday is over before you can replenish supply - or just from having less time to have the game seep into the consumer's mindset. Holiday sales tend to skew towards the more casual consumer - so by having the game out a week or two in advance, there's a greater chance that they've become aware of the game (through advertising or word-of-mouth) by the time the holiday arrives.