[sdiy] LEDs dying in LCD alphanumeric display

[Adam Inglis]

Why would the LEDs that backlight my Proteus' 2x16 LCD display slowly  
die from left to right over the course of a couple of weeks? Seems  
like an odd failure mode. The LCD works and responds to contrast  
control. The 5 volt supply for the LED circuit is separate from the  
LCD supply, but they both measure up fine.

It's one of these...
http://www.densitron.com/displays/Alphanumeric_LCD.aspx

Can you crack these open and replace the LEDs or do you replace the  
whole unit?

cheers
Adam