See about Page 9 of http://www.sanken-ele.co.jp/en/prod/library/pdf/h1-l04ec0.pdf
If you sift through it all, you see these to be about 4 to some year design life. I won't duplicate the entire content but it is normal for the brightness to fade to about 1/2 and then they call it a failure. I have an old PDA that is 7 years old and it exhibits the endstage color issue discussed in this document.
So, bottomline? Until it hit's 1/2 the original brightness it hasn't failed.
Bob
I have a 1 year old MBP. I think the screen is dimming. Does this happen. Are notebooks more likely to dim than imac or other desktops?

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