I've read multiple recipes that ask for aged egg whites, some for up to 3 days. I've tried the recipe with fresh egg whites brought up to room temperature and aged ones and didn't see a big difference. I think the most important part is that they are not cold and straight out of the refrigerator!
I've premeasured all my ingredients using a digital kitchen scale. Place a bowl onto your scales, tare the weight, which will set the scale to zero and sift the flour into the bowl. Discard any large pieces that didn't pass through.