Ultimately a situation comes about in which although the bulb is lit it does not throw much light in the room. Also, continuously ‘evaporating’ filament of tungsten may not last for a long time. A well-known American chemist named Erwin Lang-Moore invented two methods in 1913 to bring an end to both these problems: (1) He twisted the strands of tungsten filament weaving them into a plait which till now were in the form of spring like coils. Plaiting made the tungsten filament more durable. (2) He replaced the practice of leaving vacuum in the bulbs with that of filling them up with nitrogen or argon. Argon is an inert gas which does not give rise to any chemical reaction and so would not affect the working of tungsten filament. At the same time the pressure of Argon gas would almost prevent ‘evaporation’ of the filament.
It is because of the above two inventions that a present day electric bulb has useful life of about 1,000 hours.
Incandescent light bulb (Wikipedia)