Question: The question is basically it but here's the background of the story if curious:

My eyes woulld ache since I spend 12+ hours a day looking at a computer screen, so I decided to give night light a try and turned it to 70% strength. The colors were uglier than normal but I used it for about a year (always on) and now when I turn it off it looks like I'm looking at the sun when I look at my computer screen.

Anyway, my concern is, is leaving night light on long periods of time bad for my computer?

And a follow-up question if someoone knows: is always using night light bad for the eyes?

Answer: 
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> is leaving night light on long periods of time bad for my computer?
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What night light setting does is just to decrease light of display, and maybe not equally all colours, but blue is reduced a bit more then the others.

So the answer for your question is **NO**, using night light will not cause any negative effect for your display (it could even be a little beneficial for it, but I don't think that would be measurable).

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> is always using night light bad for the eyes?
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> 
> 

Having less eye strain with night light settings is definitely a good sign, that's the feedback from your eyes that it prefers those settings.
Well, it depends on the strength of the Night Light. If it's Normal then It's Beneficial for your Health but if you set it to Extreme Kinda Ultra Instinct then you need to check whether you are color blind for red because it's bad for your display as it uses the red color at its max then all time. So Just Consider the Level of Night Light and Everything is OKAY. Except for your Color accuracy If you gonna use Photoshop or Some other $h!t.