Im pro breastfeeding and most women i know bf until bub is 10-16 months of age.
That being said (and sorry if this offends but it is my personal opinion): The thought of having a school aged child suckle his/her mothers breast makes my skin crawl. At that age, I'd have concerns with the parent/child
Situation. I'd be worried about the mother: that she's breast feeding her child because she can't cope with that child growing up. God help that child dealing with their mother when they are older. Same with having grandparents bf babies, that gives me the heeby geebies. As for the WHO guidelines: they have to be applicable for the entire globe, not just wealthy western nations. The 4.5 age is mainly for kids in impoverished nations where there isn't much nutritional food to go around.