First time at 10, but by the time I was in middle school, every morning. I started with black but now have it with a dash of non-dairy creamer. I must be the only person who likes the stuff.
My parents both drink coffee, as did their families. My mom drinks 2+ pots a day. I now drink about 2 cups in the morning and sometimes a cup in the afternoon at work.
Oh, and on the growth-stunting – I got that too as I was a runty little girl and didn’t hit 5’ til I was in high school. I did top out at 5’8 though.