I have turned mine off at 3 weeks when brooding outdoors in spring, with nighttime lows in the high 50's, because they were avoiding it. I might very well start acclimating yours now, and put them outside within a week if they were mine. I'd certainly turn off the light.
They need good warmth and pampering after being shipped, certainly -- until they recover from shpping stress, which can take several days. After that, they mature rapidly.
The best way to determine how much heat they need (they don't need any artificial light, of course) is how they respond. Chick these out: