I honestly don't think it ever came up beyond preschool. My twins nursed for 5 1/2 and 6+ years, but by the time they weaned they were only nursing at night before bed. It was just part of the routine - do your kids talk to their friends about brushing their teeth? Of course, nursing is more meaningful than that, but for our kids, there's nothing remarkable about it.
My daughter's best friend, who we've only known for a year (so DD was weaned before meeting her), still nurses at 5+. And they do talk about it, but then both moms are nursing 14 month olds and they have sleepovers and the like, so my DD sees her friend nursing. I think it only comes up because we're around when she nurses.
When we talked about weaning (we talked about weaning for a LONG time
), they were really surprised to find out that most of their friends . . . okay, ALL of their friends were already weaned.