I have been turning the light on in the am, but was concerned it would keep them from going to roost if I left it on at night. Good to hear that it doesn't seem to bother them. I'll start turning it on for a little while at night, too.
I did give them a break until January, but once their molt was over, I started in with the light.
ETA - I wouldn't leave a bright light on all night, if that's what you were asking...but I have heard that a night light of some sort is good.