The early 746 backlight problem can be permanently cured by locating the transistor that controls the thing and heatsinking it.
Description here:
http://www.ham.dmz.ro/icom/ic-746-backlight.phpIf you don't do that, running at 100% backlight means the pass transistor will be running at the coolest possible temperature and should last as-is.
If you want to dim the screen and have an early model, best to do the mod.
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