Sodium stearoyl lactylate (SSL) forms strong bonds with the flour proteins during gluten development, improving dough strength. During protein denaturation at baking temperatures, these bonds weaken and SSL is able to translocate to the starch molecules, reducing their staling rates during storage 1.
Place the ice cube tray in the freezer and freeze the egg whites until firm. Pop the egg whites out and transfer them to a zip-top freezer bag and return to the freezer. Now, whenever you need one, two or three egg whites for an egg-white-only recipe, you have them, premeasured, at your disposal.
As the American Egg Board notes, the dates you see on egg cartons are not food safety dates. They are most commonly used as a guide for stores to know how long they can sell the eggs. Raw eggs will maintain their best quality for about 3 weeks after the sell by, use by, best by, or expiration date on the carton, assuming continuous refrigeration. Most cartons must also have a so-called Julian date stamped on the side, which indicates the date the eggs were packed. They will still be perfectly safe to use for at least 4 to 5 weeks after that date, provided they've been properly refrigerated and are not cracked or otherwise damaged. If you want to store your eggs for longer than five weeks, your best bet is to freeze them, following the instructions outlined here.