When they're ready to sleep through the night, they will. Â They won't before they're ready.
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My first one didn't sleep through the night by himself until he was 8 YEARS old (he had autism and a lot of issues). Â But he slept through the night just fine in our bed.
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The way we got him to STTN by himself was to borrow the neighbor's border collie (whom our son adored). We showed the dog our son's bed and said, "you'll be sleeping here tonight," and I swear, the dog nodded.  And he slept in my son's arms all night. 
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Our second baby STTN at 6 weeks. Â I went back to work when he was 9 weeks, and he didn't sleep alone through the night again until he was 2. Well, actually, he didn't sleep alone then, either--we put him in bed with his brother, and they both STTN together.
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Baby #3 also took years to STTN.
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With all of them, we didn't stress about it. Â We started putting them to bed in their own beds (we gave up on cribs early on and just put them on a futon on the floor) when they were about 1 1/2, read to them, lay with them til they fell asleep (or until we didÂ
), and told them that they could get in bed with us in the middle of the night if they needed us, BUT NOT TO WAKE US UP.
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Most mornings, we would wake up and all 3 of them would be in bed with us.
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It was actually really nice. I miss those days.Â
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I could never understand why the pediatrician would get so fired up and insist "You have to teach them to put themselves to sleep." Â WHY? Â They put themselves to sleep just fine now--what's the rush? Is there a race? Â Are they better human beings if they don't crave a parent's warm arms? Â *I* don't like to go to sleep alone, why should I expect a baby to?
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A side benefit: Â our older kids would lie down with the younger ones if we were busy--WITHOUT BEING ASKED.