Hi and welcome to Just Answer. I'm Steve, I'm sorry to hear about your issue. I will try my best to give you a precise and accurate answer.The backlighting is just that. It is an illumination source that 'lights up' the LCD screen. The level of illumination in no way affects the life of the LCD panel.
I would start at 90% and go from there.
I'll be here if you need more help.
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