I recommend serving latkes fresh within 10 minutes of frying them, if your cooking schedule permits. If you need to make them ahead, fry them 2 hours or less before serving. You can also freeze them if you're not serving them right away.
To Reheat Latkes: Place them on an ungreased, unlined cookie sheet. To reheat from room temperature, place in a 375 degree oven for about 10 minutes (7 if using a convection oven), until heated through, just prior to serving. From frozen, it can take 15-25 minutes to reheat. Sprinkle with more salt, if desired, and serve latkes with applesauce and/or sour cream (or dairy free sour cream).