Hi mamsh! Hindi lang talaga, usually siguro 2-3 weeks lang safe siya once opened, depende sa storage at kung paano mo sineseal, kaya importante i-check mo ang label ng brand mo kasi may specific instructions usually sila doon. A few of us moms, ini-throw out namin after 3 weeks to be safe, lalo na pag nakita namin na may clumping na o amoy na off, kasi di rin biro ang baby's tummy! Keep it in a cool, dry place and make sure talaga sealed tight between uses, and kung may doubts ka about freshness better discard na lang para peace of mind.