Breast feeding cut off?

I have seen breast feeding YouTube videos of women breast feeding 3 & 4 year olds.. Like that sexy spiritual mom who doesn't really breast feed them they are just playing with her boobs while she talks about nothing educational lol I'm wondering how old is enough, enough? I think my other kids breast fed up to a year.. It just doesn't seem kosher to me that my son be having full on conversation while he sucks my breasts and stands while doing it lmao is there any real educational videos out there that help with breast feeding problems?