The 30 watt heater should also last the life of the LED bulb, saving the maintenance every year or so to replace the traditional lightbulbs.

For most climates, designing in a temperature sensor to keep the light a little above freezing would pay back in well under a year of power savings.

Update: Did a quick search for LED traffic balls… looks like about 10 watts when on, and I don't see any of them integrating heaters. Market opportunity! Make LED traffic balls but add a tiny micro controller, thermistor, and a heating element, maybe attached to the existing heat sink and you are set. (Yes, attaching a heater to the heatsink sounds counterproductive, but you will be running it when the heatsink is nearly freezing so the LEDs will still have plenty of thermal differential to dump their waste heat.)