Unless a real component on the LED fails, it will provide light forever. While LEDs do not burn like fluorescent lamps and other bulbs, however they are degraded and weakened over time. The diode itself will start to emit less and less light over the years.

It is very possible that your car battery dies if you leave it on for 4 hours, but it is difficult to give exact figures on the duration of your car battery. Some people can leave their lights on for 4 hours and it will not die, some people return to a dead battery if they left it during that time.

If you leave a static image on any television for long periods, it risks burning that image to the screen. This is more likely to happen with a plasma, but it can also happen with LCDs. Generally, if you see anything else for a few hours, the blocked image will disappear.

Depends on the age of the car's battery, as well as the amount of energy the headlights derive from it. Some people may leave their lights on for 4 hours and will not die, some people return to a dead battery if they left it during that time.

If you have automatic lights for your trunk, and if you accidentally do not lock your trunk completely, the light can empty the battery. Even with the accidental exit of the car without closing the door completely. It is also common for people to feel the engine off and not realize that they have not connected the key completely.