My limit would probably be around 4.
I know people say that extended BF is for the mother's benefit and this may be partly true, but people who say that have the wrong end of the stick entirely. Right now continuing to BF is a fantastic parenting tool. It gives me an easy thing to do that works 99% of the time for calming, soothing, sleeping and comforting. Hell yes that is to my benefit because it makes my baby happier and it's less work for me. Also weaning is hard. I've got enough hard stuff to do to even consider weaning just because society thinks I ought to. I've been trying to do it, though I'd be happy to continue, but BF is preventing me ovulating.
Right now I'm my baby's comfort object. Which is fantastic in a way and exhausting in others. But if my child had a more traditional western comfort object (a blankie, dummy, teddy etc) I would be concerned if she wanted to take it to school with her (tbh I've seen people in recent years bringing blankies to university
). To me, that would mean she isn't getting some fundamental level of comfort from the rest of her life. I don't want her to have to latch on (har har), to anything, breastfeeding included, because she can't find comfort elsewhere.
As for bottle feeding after 1 vs BF after 1 the bottle feeding does not promote natural oral motions, as breastfeeding does, so can inhibit proper oral development. Cup feeding/drinking is a similar natural motion to breastfeeding so does not have this issue.