Doubling Extract Recipe

At this stage of my brewing experience I brew boxed recipes from my local HB store. My sister is getting married and I wanted to brew for the reception. I plan to brew 2 double batches from recipes I have had good luck with in the past. To make it easier, save time and be more consistent; I planned to just buy 2 boxes of each and go for it.

Do I need to worry about any "Gotchas?"

Thanks in advance!