Steve:
In the cases where I have had LCD modules with the heater (which also implies a needed temp sensor) and in those applications where a temp sensor near the LCD is available, I have arranged the LCD bias adjust to be adjustable either through a PWM or D/A. Once you have software ability to adjust the contrast, a feature that users like, then you can also apply temperature compensation for the display.

I also suspect that some of the displays that Erik and others have found faded (of the LCD variety) may have had fixed bias voltages from the circuit board with no adjustment. (This is common in many products just due to the simplicity of designing it this way. There is something that I have noticed which is that some of the fading of LCDs may be due to long term changes in the polarization of the crystals themselves. If you have an adjustable bias it is sometimes possible to compensate for the "fade" by adjusting the bias level. If you make the setting user accessible you now may extend the time till when the eventual service call may arrive due to "I can't see the display".

Michael Karas