They don't last long because the filaments are so thin. Plus, they'd never sell any new ones. :)

Yes.

All of the energy, including the small amount that becomes light, turns into heat.

Incandescent, oil filled heaters, and any device that uses resistance wire produce 100% heat. No chimney flue losses are involved. Heat is heat. It produces so much per Kilowatt hour.

Electric, with no chimney, is 100% efficient.

When you get into the meaning of 100 watts of electric heat and 100 watts of light, I defer to others.

1. All energy becomes heat. All of it.
So, the electrical energy going into a light, a fan, a stereo, etc. all becomes heat. Any electrical device is 100% efficient (close enough) at producing heat. As the previous post said, a device that has a flue will not be 100% efficient at producing heat that goes in your house... because some of it goes out the flue.

2. The electrical energy that is actually consumed by an electrical device, measured in watt hours, is the amount of heat it produces. period. The only exception to this is a heat pump. So, a 1500 watt Edenpure heater produces exactly as much heat as a 1500 watt hair dryer or 1500 watt vacuum cleaner or 15 100 watt light bulbs. The EdenPure and Solar Comfort heaters have a higher coefficient of BS and are made of special wallet lightening materials... but other than that, they produce the same number of BTU's per watt hour of electricity as my Kitchen Aid mixer.

3. Believe it or not, visual light output isn't measured in Watts as we commonly think of it (it is a measure of radiant flux). We use the amount of light an incandescent bulb produces as a common reference point, but it's a really poor reference.
So, for example, we say that a 26 watt florescent bulb produces the same light output as a 100 watt bulb... but the amount of light a 100 watt incandescent bulb produces varies a great deal. One of the factors is the voltage applied to the bulb and the voltage at which the wattage rating was given.

On the other hand, a 26 watt fluorescent bulb produces 26 watt hours of heat while a 100 watt bulb produces 100 watt hours of heat. If it's light that you are after and not heat, you want the thing that produces the most light for the least amount of electricity. A kilowatt hour (1000 watts for an hour) is equal to 3413 btu's.

BTW: large office buildings often don't need heat in the core of the building because of all the heat from the lights, computers, etc.

The actual measurement of light is very complicated - there are parts of the light spectrum that we can't see (infrared and ultraviolet, for example) The common measure you will likely see in comparing light output is lumens. That is a more apples-to-apples measure of light output for average people if you don't use the inexact "incandescent equivalent".

Given that information, can I help you narrow down your questions a little?

The wattage can be converted to btu's, which is a measure of heat.

The light emitted by a light bulb is measured in lumens.