Just to share, I used it for both kids. For my older one, I was not so consistent in using. Sometimes forget, sometimes remember. But for my 2nd kid, I was more consistent, everyday at the same time, morning and evening.
My older girl is now 2 years+. She started talking at 9 months. I counted her vocab, more than 80 words at 11 months.
My younger girl is 4 months. She is very easy to latch, easy to put to sleep. She is more eventempered than her sister. I would call her a textbook/angel type - she follows a routine everyday, so looking after her is predictable. My elder one compared to her little sister is not as easy.