For Noah it was really early, at about 2 weeks, but some babies are more adaptable than others. Cause he was bottle fed it was a lot easier too, and I found he got hungry after the same sort of amount of time, and drank pretty much the same amount. so I think we gave him feeds at set times every 3 hours or something and 4 hours at night. then gradually as he got older if he was draining a bottle we increased the amount, then spaced them apart a bit more etc. The only time we did feed at set times was at night, but his body had got into a routine from the day feeds so he always woke at the same points at night too.
See what works for you, some abies take to a routine sooner than others, if he isnt getting on with it leave it a bit longer.