No calculations , no technical values!

If the lamp is prewarmed at (say ) 10% of its rated voltage then the stress
on the filament will be reduced when full or higher voltage is applied thus
lengthening the life of the lamp?
But to what extent of the manufacturers rated life?

Technical calculations could be made as to how much the filament "coil" would
expand and contract at various absolute voltages and the type of metal/s used
for the filament.
Maybe after x thousand cycles the filament would fail due to expansion/
contraction fatigue (along with heat fatigue ) at whatever
temperature/waveform and frequency is presented to the filament.

A Squarewave would provide the harshest environment for an incandescent lamp
0 to X volts in a minimum time- Just look at  the filament! snake in a tube!

Regards

Kevin

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