With my first, I got pg when he was 17 months old. He was down to just once or twice a day (and just a few, wiggly minutes at that before he was on to bigger and better things). In fact, I pushed it a little because we were going out of town and I knew that the nursing would be convenient on our trip
When my nipples got sore around 6 weeks, I just stopped offering and he never asked again.
I nursed my second child until just a couple of weeks before her second birthday. I was getting really tired of it and she was down to less than once a day. One day I realized we'd gone 3 or 4 days without nursing and I decided we weren't going to go back. I think she asked twice after that and was easily distracted to something else.
Still nursing my youngest, she's only 11 months