Hey mama! Para sa opened formula milk, usually dapat consumed within 2 hours if nasa room temperature, or up to 24 hours kung naka-refri na, pero lagi kang dapat mag-check ng packaging ng specific brand mo para sigurado. One of my mum friends always follows the instructions sa Enfamilk container mismo, kasi bawat brand may slight differences talaga. Best to discard na lang kung hindi mo na sure kung gaano katagal na nawala, better safe than sorry with baby's feeding!