I have been applying henna to my hair since I was 18 for conditioning. Now I have a few grey hair which I hide using henna. Till now used to keep henna in hair for 4 hrs. But I read somewhere that if you keep it for 8 hrs it is better. Since last 3-4 times I have been keeping for 8 hrs without any hassle. Experienced ladies pls hlp, will this have any long term side effects like drying out of hair etc. Also how muich time should I keep on henna in hair.