As you can check in the "Please help, "Shadows" on my NEC Spectraview 2490 and 2490WUXi2, Mura effect?" thread in that same section of the forum, I just have suffering a bad experience with two NEC displays.
In my case, the professional working life of those was just over 10.000 hrs, even less if I were more exigent when the first signs of problems appeared after a year-year and a half after purchase.
What has limited their life is not the natural fade of brightness of backlightning, which remains correct and, but issues affecting LCD technology as a whole and defects in the quality-fabrication of my displays.
What I expected when I bought the NECs was over 30.000 hrs in order to amortize my investment, a reasonable figure for a supposedly professional product, but not even close to the actual performance. From that experience I only can to wish better luck to you and the advice to use your warranty rights quickly if you begin to have any problem (tolerate them focused in my work was my error, a hard lesson)
Besides, I have to mention that in my professional life including the "digital revolution" from the beginning, that type of short life in a pro display was very uncommon to me (it was a bad surprise), and I presently possess CRTs from BARCO or even Supermatch Pressview Trinitron with more than 20 yrs working fine (that is limited to serve high end scanners but bright and calibratable enough to serve their duty), making the investment done at that time one of the best of all equipment.