I've been reading about this too - seems like our baby drinks a lot (90 to 120 mls each time, every 2 odd hours at 4kgs, 3 weeks 3 days) and I was getting worried so asked the gynae. In general it's OK to feed until baby is satiated, but look out for signs of overfeeding like vomiting milk within 30 mins to an hour. If you must have some form of measurement, take body weight x 150 mls as a guide for total volume in a day then divide that by the number of feeds to get volume each feed.