1 He should be able to hold his head up and sit in a feeding chair or infant seat.  Weaning from breast milk: Your baby needs nutrients from breast milk until he is at least 12 months old. If you choose to stop breastfeeding your baby before he is 12 months old, you will need to bottle-feed him formula. His body needs the nutrients that breast milk and formula provide until he is 12 months old.
https://www.drugs.com/cg/how-long-should-i-breastfeed-and-how-do-i-wean.html
Why Preemies Might Need Special Formula. In the NICU, when preemies first start taking milk feedings, doctors start with small amounts of formula at a calorie ratio that mimics breast milk. As babies get more used to feedings, doctors may start using higher-calorie milk to help babies grow more quickly.
https://www.verywell.com/how-long-should-my-baby-use-preemie-formula-2748587
What to Do If You Want to Stop Using Preemie Formula. If there's a specific reason why you want to stop using preemie formula, talk to your doctor. Some babies do better with hypoallergenic products or lactose free mixtures, although these formulas might not have the same nutritional profile as preemie formulas.
https://www.verywell.com/how-long-should-my-baby-use-preemie-formula-2748587
How Long Should Your Baby Use Preemie Formula? If your doctor recommends NeoSure, EnfaCare, Nutriprem 2, or human milk fortifier, it's important to keep using them for as long as your doctor recommends. Depending on your baby's unique needs, that may be until your original due date or until three, six, or even 12 months later.
https://www.verywell.com/how-long-should-my-baby-use-preemie-formula-2748587
Really they should be on formula or breastmilk until they wean between 2-4 years. Cow's milk is a really poor substitute for breastmilk, cow's milk should not make up a large part of anyone's diet. There is no good reason to wean from formula or breastmilk until babies are ready to eat a diet without dairy.
https://answers.yahoo.com/question/index?qid=20070110153113AA3JCqv
Preemie formula and HMF have more calories, protein, vitamins and minerals than regular baby formula or breast milk, and are designed to help babies grow faster. Common brands of preemie formula include NeoSure (by the makers of Similac), EnfaCare (an Enfamil product), and Nutriprem 2 (by Cow & Gate).
https://www.verywell.com/how-long-should-my-baby-use-preemie-formula-2748587
Best Answer: at one year you can start to ween them off formula no sooner than that!! Most pediatricians say that you shouldn't give whole milk until at least after a year old and then they can have skim milk after 2 years old. I would say your twins should be eating quite a bit of baby food at 10 mos. old.
https://answers.yahoo.com/question/index?qid=20070110153113AA3JCqv
By 10 months of age they should be on solids, 100% juice and water which will cause them to generally consume less formula. They should remain on the formula until they are 1 yr of age. Do not give them cows milk some say it just curdles in their tummys.
https://answers.yahoo.com/question/index?qid=20070110153113AA3JCqv
If it is in the refrigerator, pre-mixed formula (also called ready-to-feed formula) that is opened must be thrown out after 48 hours. Formula that you mixed must be thrown out after 24 hours. If your baby does not drink all the formula within one hour, throw it out.
http://pregnancyandbaby.com/baby/articles/945875/top-5-baby-formula-safety-mistakes
Mistake #3: Keeping mixed formula out too long. Formula that is sitting out at room temperature must be thrown away after 1 hour. If it is in the refrigerator, pre-mixed formula (also called ready-to-feed formula) that is opened must be thrown out after 48 hours. Formula that you mixed must be thrown out after 24 hours. Mistake #4: Re-using leftover formula. If your baby does not drink all the formula within one hour, throw it out. Do not refrigerate a leftover bottle with formula with the intention of your baby drinkig it later because bacteria could make your baby sick.
http://pregnancyandbaby.com/baby/articles/945875/top-5-baby-formula-safety-mistakes
how long should a baby be on formula
A baby should be at least 12 months on formula. A baby should be on formula for at least 12 months.