In article , Tim
Smith wrote:
In article ,
(Don Klipstein) wrote:
LED's aren't at CFL prices, yet, unless you average in the 10-20 year
life.

White ones mostly have rated life of 50,000 hours.

That's 5.7 years at 24/7, but aren't light bulb lifetimes rated assuming
something like 4 or 6 hours a day or something like that, which would
indeed by around 20 years.

Although I see some compact fluorescents with limited warranties for a
specific number of years of service life in home use, the life expectancy
figures that engineers deal with and determine are usually operating
hours.

There are now LED fixtures on the market, with the "bulbs" not
replaceable. Somehow, I think of light fixtures as architecture items and
most would not want to replace them every 20 years.

I can see it now: White LEDs at 50,000 hours (or less if they are
operated aggressively to use fewer LEDs which are expensive, or if
heatsinking is skimped on) normally don't die, but at that point have
faded to 70% of their initial light output. They will usually still glow
at 100,000 hours, though probably at about half their initial brightness.
I suspect most will keep on ticking at 200,000 hours.
So those with LED light fixtures will put off replacement of fading ones
until they have light distribution pattern change by LEDs going completely
dead, or until they fade to the point of being no more efficient than
incandescent lamps. (By then, there should be plenty of economical and
super good LED light fixtures, good and economical screw-in LED bulbs,
whatever.)

However, I see some of the current and near-future LED fixtures being
the "new mercury vapor lamp", with reference to ones of "Big 3" brands
made in Europe and North America. As long as they were started
infrequently (at most once a day), they were very slow to die, and some
lived 100,000 hours. I have heard laments from some seeing these and
complaining that the companies that made them regret their long life.
However, these did fade from arc tube inner surface darkening, and kept on
ticking while producing a small fraction of their original light output.
If they were usable at 1/4 or 1/5 of initial light output, then much lower
wattage lamps should have been used with replacement after 24,000 or
whatever hours!

- Don Klipstein )