You can make deviled eggs a day or two ahead of time, but you will want to keep the egg whites and the filling separate until the day you are serving. You can store the egg whites in a container with a tight lid or wrapped in plastic wrap in the refrigerator and keep the pre-made filling in a plastic bag with air squeezed out or in a tightly sealed pastry bag. When you are ready to serve, put the egg whites on your serving platter and and add the filling. Once filled, the eggs can be stored, covered, in the fridge for a few hours, but it is best to serve them as soon as possible.