World's oldest light bulb

[beam me up schottky]

The bulb in the ceiling rose in my bedroom has been in use for about 18 years, it runs through a dimmer so whenever switched on it gets a soft start and almost never runs at full power. If it lasts another 92 years I'll let you all know

[Skywave]

Power-cycling and life expectancy: indeed, Jamie, that is a valid point.

I'm not too sure about the filament material in this particular bulb, but basic Physics tells us that the resistance of most conductors increases when they get hot - ignoring Thermistors, for the time being. So when the filament is cold, the resistance is low, the bulb is switched on, there is a surge of current, the filament gets hot & glows, the resistance increases, the current drops. I suspect that the lower the rate of rise of current, the longer the bulb will last - simply because under those conditions, the filament is under less dynamic electrical & mechanical stress.

In a parallel vein, when I used to be a Field Service Computer Equipment Technician, I used to look after about several hundred VDUs at one particular site. Some of these did a daily rota of 'on' for 8 hours, 'off' for 16. However, a few were switched on 24 / 7 / 365. Piece and part of my job was to write monthly reports on Service Calls, etc. One of the statistics I was required to deliver was MTBF. The 'daily use' terminals returned an average figure of about 15,000 hours; the 'always on' units figure was in excess of 200,000 hours! I hardly ever saw those - and when I did, the 'reported fault' was nearly always a fault in a piece of kit that was external to the VDU, but to the non-technical user it looked like a VDU failure. The most commonest (valid) call was simply to replace worn-out CRTs!

Al.