My monkeys are all teenagers. While they have been trained, trained again, and retrained, they are still teenagers. They occasionally leave things on they have been trained to turn off or leave things out they have been trained to put away. Minimizing the possibility for mishap has served me well over the years.
As far as using the light without the iginition on or the engine running, I probably wouldn't be comfortable doing something like that for more than 10-15 minutes tops. And even then, I'd probably rather run the engine for that 10-15 minutes when operating something like a spotlight. Furthermore, if I were doing a job that required lighting for significantly longer, I'd either do it during the day or probably run a generator.
I'll post a pic or two when the installation is done.