I have once again reached the point where one box of hair dye will simply not be sufficient. My hair is barely past my shoulders (by about 2 inches) and it's T-H-I-C-K. So thick, the bottle of hair dye I used just now was sputtering and running out just as I was finishing up the crown of my head.
Whew!!! But by the time I dye again, I'll probably need a second box . . . just so I can be totally thorough.