My grandson is 4 month old, taking the Nestle NAN1. Recently he had cold, nose block and quite frequent could not finish taking the milk prepared for him. I would like to know how long can I keep the unfinished milk for the next feed, 1 hour, 2 hour or more? vasu replied. Though I personally prepare fresh formula to give my baby each time but my friends make and store till 1 hr previous to each feed time and they says their doc was fine with it. Elizabeth replied. Hi! I do not recommend storing unfinished milk. It will always be best to feed the baby freshly prepared milks regardless of the baby’s age. If the baby iss unable to consume the milk you prepared in one feeding, better discard what is left. Unfinished milks can be contaminated by harmful bacteria and can cause illness. So if your baby’s not feeling well and is unable to consume his or her usual milk preparation in one feeding, try to reduce the preparation so left overs are avoided. Give the baby small frequent feedings of freshly prepared milk.