I think of it simply. At 8 weeks your grafts are normal functioning hair follicles. They are just in the telogen phase. If what you do would affect your hair before transplant it probably will affect the hair that has been placed in a different position on your head. Chances are you have had a few nights out before the transplant and had no impact on your hair. Obviously heavy regular drinking would wreak havoc on your body's nutrients, minerals, etc. and you could expect all of your hair to become brittle, etc.