From what I've read, in more natural societies it's not unusual for children to breastfeed until about age 7. Of course, by then they are getting most of their nutrients, by far, from other sources so I guess it's mainly for occasional emotional support.
Our modern society has definitely perverted breastfeeding into something with sexual undertones. That's dysfunctional and harmful and far more common than advanced age breastfeeding.
However, one wonders who the continued breastfeeding beyond maybe age three is for, the child or the mother? It does seem to smack of someone who doesn't have enough in their life and wants attention for being "super mom" or who is too much clinging to their child continuing to be a baby.
Personally, I stopped breastfeeding for a short time when my older one was about 18 months old because I was heavily pregnant with another baby. The breastfeeding was making me have contractions, which I didn't want to mess around with. After the second baby was born, I breastfed them both for a short time. But the first child, having already had a break from it, soon seemed done with it anyway. Then I continued to breastfeed the second child until around two or two and a half, though by then of course it was just a couple of times a day, nowhere near a main food supply. I didn't have any end date in mind but just kind of let it end when the baby no longer seemed that interested.
Anyway, I wouldn't mind going against the grain for a good reason but I also do find extremes suspect, when there's no clear reason for it and it's far outside the norm. Personally, I'd say five is too much and that it would be a good time to move on to another childhood stage now instead of being overly invested in it.