I've again seen another segment on Defense TV with Clint Smith recommending at least 3 Tac lights be on hand for emergency deployment. (Quote: "One's good, two's better and three's best....)
Of course, most of us are lucky to have just a single Tac light available when the chips are down and we need to move and possibly fight in an enclosed room event. My SureFire is always ready to go on the bedroom nightstand and if I can get to it, my AR carbine has a similar tac light mounted. I guess two out of three aint bad....
US Night Vision Corporation