My LO is 18 weeks this wk and from last wk we have been aiming for 3hr 45/4hr easy.
This is what we were doing at 3.5hrs easy
7am, 10.30, 2pm, 5.30, 7.30 top up and 10.30 df
He usually has 6oz and 4/5oz top up at 7.30 making a total of 35oz.
He doesn't have any night feeds.
HTH