I let my girls decide when they were ready to night wean. I honestly can't remember what happened with Meg. I think it was around 15 - 18 months. She just gradually stopped waking up as often.
With Abbey, night nursing was the last to go. She was about 3 before we gave it up.
Kayla was completely weaned by 9 months. She was more of a biter than a nurser. when I would bring her into my bed at night for a few minutes of cuddling, I'd keep a blanket between us so she wouldn't try to bite. We had a few weeks of really rough nights but I felt like I had to do it. She was drawing blood with those little vampire teeth!
It helped I think that we never co-slept. The crib was right next to our bed but not side carried. (I didn't know you could do that.

) So they couldn't smell me really and waking up to nurse was a bit more of an ordeal for both of us so we never had the marathon nursing sessions. I don't think any of my girls woke up more than 2 times a night by the time they were a year old.