The panels themselves can last a significant amount of time, up to the number you specified. The numbers you noted are actually more in your favor, considering most stores turn off their electronics at night.

Naturally, this isn't to say that things can't go wrong, or that other components besides the LCD don't age - or couldn't malfunction over time, but all things considered, getting almost half off the retail price for less than 10% of the life of the TV is still a pretty good value; at least, I think most people would agree.