I was blond, then I colord my hair brown, how many times should I color myself till it stops fading?

A family friend is a dark brown she colors her hair red she only has to color hers about every 6 months to a year because she colored it so much she can use the dollar store brand and it will last the same amount of time hers doesn't fade to much you can just see some of her natural color coming out just color it with the best brands until it stops fading so quickly and then you'll be able to use any brands you want to every 6 months to a year everyone's hair is different to different colors and brands so just take your time and see what works best on your hair it took her a good while to get to where she can color it only once to twice a year