I have 2 kids, a bled for two weeks after giving birth. And then I had no period at all for 3 months. With both kids.
My sister-in-law also has two kids. She bled for 3 weeks after her first baby was born. When she gave birth to the second, the doctors did a curettage afterwards, because the placenta wasn't complete and they feared she'd get an uterus inflammation. Then she only bled for one day.
It can last anywhere from two weeks to six weeks, and it's never quite the same. I had 6 weeks for my first, and only 2 weeks for the next two.