DS nursed for approximately 49 months (he gradually tapered off and stopped about a month after he turned 4). DD is still going strong at 18 months, but I'll surprised if she goes as long since she's not as much of a comfort nurser as DS was (he wanted to nurse every time he got a little bit upset).
So that makes 67 months and counting.
I'm thankful that I haven't had to work for pay during this time. I did go on some overnight and multi day trips when DS was nursing, and pumped during that time until he was about 2. After that I found I could go up to three days without nursing or pumping and be fine. DD has never accepted pumped milk and has so far refused any milk except mine, so I haven't pumped for her in a long time and haven't left her overnight.
My kids were six years apart, so I never tandem nursed. I have nothing but admiration for those who tandem nurse and those who manage to nurse for more than a few months while working outside the home.