I have always plugged my safe light into my timer so it went off when the enlarger came on. But in a darkroom class I took last year the safe light stayed on all the time. It didn't seem to fog the paper or cause any trouble. I am working on a new darkroom and doing my planning of where everything should be placed and how to wire the room.
work on their own. It is so much apart of life that the full environment is active in what we do. And much of it hides in the circumstances quite well.