As my baby is having issue with drinking, she was drinking 100ml every 3hourly. Sometimes doesn’t finish her feed. You can try to drag the feed like feed 4 hourly and see how’s the baby doing. If your baby will give you cue when they are hungry den you may go on to feed on demand otherwise I will recommend you to feed on schedule so as not to dehydrate them. Do bear in mind that as you have been feeding this much for quite some time, if you give too little, your baby may not feel satisfied.