My two are the same ages as Mallory's kids, and both are still nursing. My oldest, though, usually only nurses once a day (at bedtime). Occasionally throughout the day if she is upset, etc., but that only happens at most once a week.
Up until about 3 months ago, she was also nursing in the morning and a couple of times throughout the day. She's just kind of dropped those nursing sessions on her own.
The youngest probably nurses 4-5 times a day, give or take.
It wouldn't surprise me if the oldest self-weans by the time she is 4 - which would be fine with me, as I'm pregnant and it would be nice not to be nursing 3! We'll see, though...