It’s funny how different my daughters are. I stopped breastfeeding with my first one when she was 4 months. It was not on purpose, but she was just too lazy to. Seriously, I just started noticing her keeping the breast in the mouth, doing nothing. Chilling lets say :))
At the end of the 4th month she stopped eating at all and we switched. With my second one we could not make her stop till the age of 2.2. I stopped just because got to the car accident and was in the hospital for months. She was crying for a couple of months more, asking me to breastfeed… I think the average should be the year or so, but I do not find it wrong to breastfeed as long as you can. It is healthy and natural. Of course, I do not find it right to breastfeed when the baby is 4 years old either. At that age the baby is not even a baby anymore. But still, breastfeed as long as you can, it will make the baby stronger and healthier! Anyway, I do not think a lot women are even capable of that. A lot find it hard to breastfeed at some point and do not even have milk anymore after a couple of months. So, if you are lucky enough, go for it and use the chance.