An incandescent filament, through the glass. SyamAstro, public domain. Not ours yet.The Centennial Light, Livermore, 2016. Gazebo, CC BY-SA. Not ours; nobody's is.

The Forever Bulb

Rated life: 100,000 hours.

Don't turn it off.

This one has been on for0:00:00

100,000hours

120 V / 4 W / E26 / 100,000 h

Specification	proposed
Lamp	General service incandescent
Base	E26 (E27 for 230 V markets)
Voltage	120 V or 230 V
Power	4 W
Filament	Heavy-gauge, run well below its rated temperature
Rated life	100,000 hours. Eleven years, continuously.
Made by	Nobody, yet

The trade-off is real and it is the whole design: a filament run cooler lasts far longer and gives less light per watt. A bulb like this is dim by modern standards and does not care.

The specification is a proposal until somebody manufactures it. The one number we can point to is below, and it is not ours.

Livermore, California

A bulb at Fire Station 6 has been burning since 1901.

Hand-blown glass and a carbon filament, made by the Shelby Electric Company of Shelby, Ohio, in the 1890s. It was first hung in 1901 and has moved with the fire department three times. It now runs at about four watts, and has been off only for power cuts and the moves. A webcam has pointed at it since 2001; the first webcam failed before the bulb did.

Sources: Centennial Light Committee, Livermore-Pleasanton Fire Department; Wikipedia, Centennial Light; Guinness World Records, longest-burning light bulb.

Decided against, 1924

What it was: The Phoebus cartel: a company registered in Geneva by the major lamp manufacturers, among them Osram, Philips, General Electric's overseas group and Associated Electrical Industries, to divide the world market for incandescent lamps.
The agreement: The Convention for the Development and Progress of the International Incandescent Electric Lamp Industry, signed 20 December 1924, in force from 1 January 1925.
The target: A standard life of 1,000 hours for general service lamps. Members' lamps were tested centrally; lamps that lasted longer than the standard drew fines, scaled to how far over they ran.
What happened: Lamp life, which had passed 2,500 hours in the early 1920s, fell back toward 1,000 and stayed there. The cartel ran until the Second World War broke it up in 1939 and 1940.

A thousand hours was not a limit of physics.

Documented from the cartel's own records in Markus Krajewski, The Great Lightbulb Conspiracy, IEEE Spectrum, 24 September 2014, and in the Landesarchiv Berlin. Nothing here is inferred beyond those documents.