This is a common question we get asked, and the answer might surprise us. Black hair dye can actually last quite a long time; however, proper care is required. Avoid washing your hair too often. Use a color-safe shampoo and conditioner. Be gentle with your hair overall. Touch up your roots every few weeks. With proper care, black hair dye can last for several months. But if it’s fading sooner than you’d like, consider switching to a semi-permanent or demi-permanent formula. These dyes last a bit longer and are less damaging to the hair.