G always took between 4-6oz from when he was about 2mo until he was... well, I don't actually remember the last time we offered... probably 9 or 10mo. He's always been in the upper percentiles (I think 75/80 is as low as he's gone), though not sure that makes a difference. Baby C only ever took about 4oz (and did so only from 6-10/11 weeks

).
I think I always started by offering about 4oz and DH and my mom told me G drained it every time, so then we offered more.