I was born in '85 (sisters were born in '87, '89, '93, and '96) and we were all BF for 4-6ish months. I'm pretty sure I was closer to 6mo when I weaned but she weaned my youngest sister at only 4mo because she was nursing "too much".
My mom still to this day believes that babies are supposed to be weaned around the time that their teeth come in and/or when they stop sitting still for nursing sessions.
She told my sister that her baby was ready to wean at 7mo because he would get distracted sometimes while nursing. Umm, hello, do you think he'd be any less distracted if that were a bottle in his mouth instead? (ETA: My sister knows that is BS, of course. Her baby is 12mo and still mostly EBF.)
And all of this is quite surprising coming from my mom because my grandmother breastfed her and her twin until they were 2.5 (they were born in '64)!