I keep a 2001 vintage Night Buster 8X which has 8 LEDs and runs on 3 AA's. Plus an extra set of batteries.
LED technology changed so fast that the Night Buster 8X quickly became a dinosaur. Newer lights run brighter and longer, have better beams, and are smaller. Since it has no monetary value, I don't mind leaving in the car where a dishonest parking-jockey, car-wash dude, service-guy, or other may swipe it.
I wouldn't risk any of my good lights in the car. You guys are trusting souls. Besides, I'm never without a good EDC in my pocket. Do any of you go out "naked"?
W.