I'm still questioning the origins of that term!
Anyway, back to the topic - the ABA literature says that with no dummy use, BFing on demand and through the night should keep ovulation at bay. Also, co-sleeping mama's have longer ovulation-free periods - must keep the maternal hormones in higher concentrations to be skin to skin. All co-sleeping mummies I know have not ovulated for at least 3 years, so them's fair apples!
We still co-sleep, BF on demand and through the night (but we DO use a dummy, only to keep him asleep after he has fed to sleep), and it's been well over two years since ovulation - I am on the mini-pill and often miss days, let alone the three hour grace period...and no pg thus far! Not to say it's foolproof, just that it's worked thus far for us and if we fall pg tomorrow, no big deal, DS will be the minimum ideal age in time for next baby
We co-slept/sleep and i got AF at 3 months post birth and we were BF HOURLY.

I would NEVER rely on BF unless you don't mind another baby soon because i don't believe its a guarantee at all