How often should I dye my hair?

Since my 40s, gray hairs have been gradually appearing; I used to pluck a few, but now they are coming in uncontrollably and in large numbers.

It's been three weeks since I dyed my hair, but I need to do it again. ㅠ

I heard that hair dye is bad, so I hope that a harmless hair dye that is not harmful to the body will be developed soon.