Life of.....

LCD....TFT....same thing.

Longevity
The only item that ages on an LCD monitor is the backlight, which is composed of one or more tiny fluorescent tubes. The typical life of a backlight is 50,000 hours to the half brightness point-the point at which brightness is one-half of the original brightness, and the industry standard measure for product life.

A CRT ages in two ways: An oxide layer forms on the cathode of the electron gun, decreasing beam current; and the phosphor ages and becomes less efficient. The typical CRT half-brightness point occurs between 10,000 and 20,000 hours.

Click to expand...

LCD/TFTs also suffer from dead pixels.
Can be due to age or otherwise.
They are also not covered under warranty.
Plus, the monitor loses resale value in such conditions.
Be certain to check for these when you are buying a new monitor.
As a rule, cheapos develop dead pixels with greater ease.
P.S. Your colored mobile is also prone to develop such problems.

As such the frequency of dead pixels is variable and don't necessarily mean your monitor is dying. but they are irritating if noticeable and cannot be repaired.

CRTs, you can tell when the picture tube starts failing to deliver , you get all sorts of problems with color, brightness or contrast ; picture may be shaky or it just dies all of a sudden.
CRT picture tubes usually last 7 years or so and certainly die after 10 years(more often than not).
LCDs manage 10 years plus without many problems (if its branded).

are TFT LCD use and throw !! can they be repaired also

dead pixels can't be repaired.
There is an excellent parallel thread on how to buy an LCD in this forum
*www.thinkdigit.com/forum/showthread.php?t=43436

thanks for the link!!

If one has got some good warranty plan, then one can get a replacement on that monitor. I'm not sure if dell does this, but Sony offers replacement on their ClearBrite tech monitors if it has 7 or more dead pixels....