Ever heard of signal bounce? Slim chance, better than none. Maybe it's a hazy day, oh, i dunno, like when a front comes through. Your potential rescuer would be easily visible on a clear day, but not in the fog, spray, rain, or chop. Waiting til you see a potential rescuer is bad advice, not to mention at night. Maybe a potential rescuer is close, but they were beat up too and their lights are out. See them? Not likely. What are you saving the batteries for? Hypothermia is closing in, fatigue, drowning. Just how long are you gonna outlast the batteries? You don't want to wail on it constantly, but judicious use is your best bet.