When they are chicks, I always let mine eat 24x7. However, once they get 3 weeks old and move out of the brooder and into the tractor/pen, they all go to sleep at night. While they're sleeping, they're not eating. However, if you have lights on them continuously, they will be less inclined to sleep, and more inclined to eat all day long.
So... I try to make sure they always have food. Even so, every morning when I fill up the trough again they all go nuts, as if they've been starving.
Temps: 90-95 degrees somewhere in the brooder for the first week. It doesn't have to be (and probably shouldn't be) everywhere. If it gets little hotter or a little colder at times, they shouldn't just drop dead. Just keep a thermometer near the heat source as a guide. If they're all huddled up directly under the heat-lamp it's too cold. If no one is near the lamp, and most are laying around with a leg stretched-out, it's too hot. I obsessed over temperatures my first couple batches. But a few mistakes later, I've realized that they're not nearly as fragile as I thought (in that regard).
Anyway, after the first week, start dropping the temps down a bit. By the end of the second week, they should be able to survive down to 55 degrees, and by the end of the third week, down to 35. So just move the lamp up daily. Since it's summer now, it's probably not going to drop below the 50's in your brooder, even if the light burned out.
Space: They grow quickly. You can easily fit 50 day-old chicks in a 20 sqft space, but 50 3 week old chicks won't. 1 sqft per chick up to 3 weeks should be more than enough though, though.
