Re: the balancing of the light bulb
The design of the incandescent light bulb is a balance between life and efficiency. The "100 year bulbs" you read about are old designs that burn dimly and use a lot of power. They have a filament you could pull a truck with.
The thinner the filament, the more light you get for less power, but the easier the filament breaks. A manufacturer must arrive at an acceptable balance between bulb life and brightness for a given wattage. A lot of engineering and materials work has gone into this over the years.