I think the OP may be referring to organic LCD panels, which do decay over time, and the rate of decay can be affected by heat, which is always an issue with PJs.
AFAIK, latest generation LCD panels are inorganic, and don't suffer this problem.
But as the OP will not need to replace the bulb for 8 years or so, it's likely a new PJ would be a good idea, as per Mr. Frog's suggestion.