We've done it numerous times
and it truly works!!
Molly has done the habitual waking at 9 - 9:30 pm for about the past 6 months. She goes in spurts though. She will wake at that time EVERY NIGHT for about a week or two, and then we do the W2S and it stops. Then a week or two down the line, she starts it all over again
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Make sure you do the W2S for 3 consecutive nights though. We have tried it for 1 or 2 and it doesn't work. The three consecutive nights allows the night time biorhythms to be reset (or something like that) so that they sleep straight through.