When is it safe to turn off the heat lamps?

[Uzuri]

I did something unusual. My chicks were in an area that was dark except for their lamp. To wean them off the light, I turned the light out during the day once the daylight temperatures were warm enough, and left it on at night. Then I swapped to a low wattage/low temp light that was just on during the daytime when the nights got warm enough, to get them back into the same time zone as the rest of us

It seems to have worked. They're all big chunky buggers now.