It's been almost 12 years

since ds1 was born at 30 weeks. He was fed through IV for about a week, and they started tube feds of bm toward the end of that week as well. He was then tube fed every 3 hr, adding bottle feeds around 3-4 weeks (it's a haze), until he was discharged about 6 weeks later. The first few days was diluted bm, then straight bm, then mixed with HMF (for calories but also to stretch bm so that it was avail for every feed). I was encouraged to allow him to root, latch, and bf any time he was well enough to be out and held. Those didn't count as regular feeds--although it was noted in his charts--they were considered bonus calories. We went to bottle feeds as opposed to breast at first because his suck was plainly discoordinated and weak. We discovered somewhere in there he had a heart defect (not PDA, but 2 VSDs and an ASD) and months later that he had mild CP. Had he been able to nurse well, they would have gradually replaced bottle feeds with nursing feeds, with a pre and post weigh in the same diaper. Even with bottle and tube feed, we pre/post weighed in the same diaper. Tube/bottles were done on schedule, bf was on demand, with mouthing encouraged after bottle feeds if he was awake. They often had me hand express a few drops and just get him to lick, to learn/assoc the breast with his food. They also encouraged finger (if dh or I were there) or paci sucking while tube feeding to associate sucking with a full feeling. As far as time limits, he had 45 minutes to take 2 oz, before he was considered negative calories, so pretty liberal. I was told that bf is less calorie demanding than traditional bottle feeding, but that with a preemie nipple, that it was easier o nthen. We could press on the nipple slightly and drip feed when he got tired, so he was doing nothing but swallowing. When we worked to get him to breast, which took 5m, we used a progression of harder and harder to use nipples until bf was easier to him and he preferred it. With this approach, ds never went below his birthweight!!!, and gained 2 whole lbs before discharge at 36w gestational age, despite the heart problem.
FWIW, our NICU was very bf friendly, had an LC that was also a NICU nurse, and taught me to pump, helped me rent one, and kept a pump kit in his basket and a pump in family/nursing room. They had rockers and privacy screens. They held the babies for all bottle feeds, and at least touched them if they were too fragile to be held during tube feedings. The 3 hr schedule had a 30 minute window, so they would feed the awake and rooting babies first, then wake the sleeping ones. Ds often ate about every 2 hr, a similar schedule to when he came home. Realistically, it is exceptionally hard to do all demand feeding on a whole room of babies that need extra attention and time for each feed, especially if you actually hold them. I spent about 8hr a day there the whole time, so I really got a chance to see that these women worked really hard to make it as natural as possible!