nan pro opened pack can be used for how many days.i opened it on 1 feb 17.i am using only 1 spoon ie 30 ml per day. to make practise to drink with bottle. today 3 weeks gets over.but its taste is same . can i use for my baby for another week. as i am using little quantity.and i packed it tight.is there any harm for baby as it wriiten on box it can be used for 3 weeks from opening date. please help me as more than half powder is remaining .