This technique worked well for us too. Four kids all sleeping 12 hours/night within the first few months (can't remember how many, but 2-5 sounds about right)
Also worth noting: all kids are different and develop different skills at different ages. The variance on the age at which kids learn things like talking, walking, toilet training etc is huge, years sometimes. If your kids early at something, doesn't mean they're smart, and if they're later developing doesn't mean they're dumb.
Also worth noting: all kids are different and develop different skills at different ages. The variance on the age at which kids learn things like talking, walking, toilet training etc is huge, years sometimes. If your kids early at something, doesn't mean they're smart, and if they're later developing doesn't mean they're dumb.