Economic Life (useful) of a Light Bulb

The Economic or useful Life of a light bulb is number of hours a batch of bulbs will operate before it is economically and aesthetically needed for them to be relamp (typically 60% to 75% of rated life). Light Bulbs tend to color shift and might not be pleasing to the naked eye after this time.

Bulb Ballast typically 2-5 times as long as the lamp. (i.e. Sign Ballast)