Hi J.! First of all I did breastfeed my daughter all the way until two months before my son was born, and I was high risk, but everything worked out fine. My daughter slept with us also, so her night waking to feed was more of a habit and not a necessity. Once I learned that after about six months they no longer need the feeding in the middle of the night, I decided to put a stop to it. So, everytime she would wake up in the middle of the night I would lay her back down. At first she would cry, but then she went back to sleep. We did this for about a week and then she realized she wasn't going to get any milk, then she started sleeping through the night.
Concerning the self-weaning, I don't know if children can self-motivate if they aren't motivated first by the parents. My children are fourteen months apart and I had decided that I was only going to breastfeed for a year before I even got pregnant. So, it was a choice/necessity for me to stop. I was getting bigger and it was an inconvience for both of us. So, once she turned a year I just stopped her. I gave her whole milk in a bottle and after having a stomach bug and throwing it up for about a week, she was fine. My doctor told me something that was so true. It's really harder on us as parents to let the baby stages go than it is on the children. We had to take her off the pacifier at the same time, and put her in her own bed, so there was a lot of changes going on, but she responded favorably to all of them. The younger they are, the more adaptable they are. We just think we are being so cruel, but in the end it's better for everyone. Hope this helped a little bit.
***Side note...Like I said I nursed my daughter for a year, and two months later my son was born, so I was a little burnt out. He came seven weeks early and I wasn't ready to start nursing again. So, I ended up not nursing him really at all...everyone's different, but you might consider stopping him sooner rather than later, to give yourself time, so you're not burned out as well.