On Thu, 12 Apr 2007 04:55:30 -0500, "Anthony Fremont"
Gave us:

Chances are that the
display was only being driven by 12V. Just imagine how long they would last
in a vehicle seeing 14V all the time.

If the drive circuit was designed properly, they should be able to be
the same brightness for a voltage range of say 7 to 16 volts. That
would be what a good designer would build anyway. A regulated front
end on the circuit would be required to achieve any repeatability with
the final product.