Mine were around 2 weeks old when I put them in the coop and about 3 weeks when I let free range.
They were just like kids at that age. They would play in the yard, run back into the coop, dive into the feed, grab a few gulps of water and then like a flash back out into yard. They would do this all day.
Now that they are going on 13 ~ 14 weeks they mainly stay out and only every once in a while go back in the coop for some feed and drink - mainly on vary hot days. So, I would have to say 4 to 5 months as well is when I would the feed consumption go down.
My oldest ones hardly eat any of the feed now, there are just too many good bugs, lizards and greens in the yard, but they will sometimes just before roosting for the night, will grab a little feed.