Well, in the last picture I posted, its been in my hair for maybe a month a half? The color actually stuck a hell of a lot better than I thought it would, even if it has gone a bit greenish. By now Cotton Candy Pink would have been back to blonde with maybe a few spots of peach.
Though, keep in my mind that I wash my hair in cool water, using sulfate-free shampoo and conditioner, and even that I only do about twice a week. I’m not sure how well it would stay in if you’re someone who washes your hair say, every (other) day with a sulfate-loaded shampoo.