I breasted for a combination of about 7 years and my nipples have never left! I vaguely remember the days before endless breastfeeding when my nipples were flat and invisible under clothing (when not in use as baby feeders or sexy body parts). They just used to ... flatten.
Now they are ALWAYS pleased to be out and about
and I sort of like that, even though it can get a bit sore in very cold weather or if there's a lot of friction. I mostly wear a bra out of the house but will take it off most evenings. But even through a bra with a little bit of padding, you can see my nipples. They just never go down, and I honestly don't mind that.
I always thought it was the US that was paranoid about visible nipples though, I didn't realise we were oddly prudish about them here.