We don't have a routine as such, but there is a pattern.
Most of the time S will go 3 hours between feeds during day and 3 or 4 hours during the night. He feeds for 30 - 60 minutes each time, so I always end up offering both breasts.
From 5pm to 9ish he likes to feed all the time - if I can find a moment where he is settled enough I give him a bath and quick oil massage. If not I top and tail. On a good day he is asleep and in basket by 930/10am (usually has to fall asleep being held).
Then feeds 11/12pm, 3/4am, 6/7am and 9/10am. After the 9/10am feed I top and tail, then dress him for the day.
However there are plenty of times when he wants feeding after 2 hours, and the odd occasion when he goes 5 hours. So it is all still pretty unpredictable, but (as I keep telling DH) he is only 4 weeks old!