With my first 3 babies I got it back around 6ish months and it was irregular until they were around 10-12 months.
With baby #4 I got it at 8 weeks

He's exclusively BF, no pacis, cosleeps, etc. I wasn't sure when I had the one at 8 weeks, although it totally felt like a period vs pp bleeding. I was sure though when I had the same thing happen 34 days later following my normal PMS symptoms. He sleeps really well, I'm pretty sure thats why.
We practice NFP so I have started charting again as my DH doesn't want any more. I had hoped we'd be able to use LAM for awhile before deciding on anything permanent because honestly I'm not 100% sure about being done.