Anything can happen, but Consistency is Key.

[Dr.Henry_Killinger]

fighter said:

Now you may be thinking, but Henry, if the last two months can outsell the rest of the year, then doesn't that prove that a short burst of sales can make up for the sales of the rest of the year?

On the contrary, it means that the sales in the Holiday period are mediated by the performance during the longer Else period, in other words, the consistent performance of the Else Period matters just as much as the holidays. 

I don't disagree with the general point, but OP is hardly making a logical demonstration, especially with this unfounded "on the contrary"

How is it unfounded? The worse the performance in the first 10 months, the better the performance must be in the holidays to make up for it. Its basic arithmetic. In simpler terms if you get C at the end of the year which is A(Else) + B(Holiday). The smaller A gets, the bigger B must be just to maintain C, let alone increase it.