Here in New England this time of year, heat stress is not a concern. I second what duckyfromoz said - if the weather is beastly hot, they need to be able to drink and if possible, get wet.
But since right now the weather is quite chilly, my runners do without food and water overnight - 6 to 8 hours' worth, but not before they were a full six weeks old. Up to then, it was 24/7 with food and water, and many brooder cleanups.
We are getting ready to move them outdoors so they will have a plywood house and attached night pen. Food and water will be in the night pen. The first few nights, though, I may just close them into the house. I am nervous about predators, even though I am trying to incorporate every solution in the book (okay, not EVERY solution) to avoid tragedy.
But I digress . . . short recap - after 6 or 7 weeks old, if they aren't in a heat stress situation is my approach.