Soft, spreadable butter does not have to mean leaving your entire supply unrefrigerated. Salted butter’s high fat content, relatively low moisture, and added salt make it less hospitable to bacterial growth than many other dairy foods, but they do not make it spoilproof. In a cool kitchen, keep only a small amount in a clean, covered butter dish, aiming to finish it within one to two days. If the room is hot, refrigeration is the better choice.
Keep the remaining butter refrigerated and well wrapped to help preserve its quality. Position any countertop portion away from the stove, sunny windows, and other heat sources; a lid limits exposure but cannot compensate for excessive warmth. Use clean utensils, and wash the dish before replenishing it. Discard butter with mold, an unusual smell, or other signs of spoilage. A modest portion offers the convenience you want without unnecessarily exposing the whole supply.