I bottle fed by demand, however it soon turned into a routine if that makes sense?

My DS fed every 4 hours on the dot. DD1 fed every 2 hours, small feeds though - about 50ml till she was about 4 or 5 months old?

DD2 feeds every 3.5 hours except for her last feed, which is only about 2 hours after the one before.

They set themselves into this routine, I don't try and lengthen the feeds out or anything - I just go with what they want.