Ah... good question! One thing I've noticed, no two women are the same!
For me...never had ppaf after #1! We caught that first eggie. #1 ds was about 14 months.
After #2 was a mess. #2 bf until he was almost 4. Had off and on breakthrough bleeding from about 24 months pp until I got fed up and saw dr a year later. He had me try charting to see what my messed up cy were doing, and if
I was even o-ing... well, we got a

that first chart, lol.
Ppaf came about 18 to 20 months after #s 3 and 4.
Now here I am, 11 months and still no sign of

.
So I guess I average a year and a half to two years. Really, though, it was basically when bf stopped. Which I don't plan on doing any time soon, lol.
But I seem to be the exception 'round here.