A friend of mine (mid 30s now) wanted to take part in a medical study recently. Part of the criteria was that you had to have been breastfed for at least 6 months. He wasn't but tried to fib his way in. They tested his gut and found he had not been, so he couldn't take part.
I can only conclude it has some effect on your gut which is measurable even 30 years later 🤷♀️
I bf my daughter until 2.5. No real difference in her compared to other kids except I'd say there is a special bond that grows between you and your baby/toddler, based off breastfeeding. Not saying you can't have that with ff kids, but it obviously will just be different.
Oh and I'm pregnant again and whenever the midwives ask about how my first was fed, I get a lot of approving smiles and nods from them when I say how long, like I'm in a special club. It can be a bit culty sometimes. Especially as she got older at baby/toddler groups, I found myself seeking out the other mums still doing it just to be able to have a chat about the various challenges of extended breastfeeding. They became fewer and fewer until eventually it was just me. I was that weirdo. I went out for drinks with a group of mums when she was about 18 months and one mum said "once your baby can ask for boob it just starts getting creepy and weird"... I was there like "oh man, she's been asking for months now... do people really think that's creepy and weird?"
Other things to consider: bf mums need to think about what they're wearing everyday. You need boob access. Obvious when they're small but gets a bit tiring once they're nearly a year. And you're in maternity bras for most of that time too. Oh and I had to wear nursing pads until she was nearly a year or I'd leak. Things like child free weddings or just evening social events without baby can be a pain because not all bf babies will take a bottle and not all mums can pump and that just causes stress. And people will tell you "just pump!" Like there's anything "just" about it.
I'm moaning a lot here but I wouldn't have changed it for the world. It was really special. Again, not saying you can't get that with formula and the plan with our second is certainly to combi feed as I am concerned about juggling breastfeeding with toddler but I'm glad I did it once for the experience.