hair does stop growing at a certain point. it's called terminal hair length and it's different for everyone depending on genetics. it's based on the natural cycle of the hair follicle where it grows for a period of time then stops growing and maintains, and then ultimately it falls from the follicle, naturally.

for some people it is very very long and for others it's not that long. you can't really do much to grow your hair longer than your terminal length. what you can do is protect and nourish your hair so that it doesn't prematurely break mid strand.

my hair is long, past my butt. I think it's hit terminal length now but we'll see.