We've done bath, boob, bed since about two weeks - don't know if it works but we did it with dd1 and she is brilliant at going to bed.
At about 4 weeks we started our routine about 9.30, by 6 weeks we started at 9pm, 8 weeks about 8.15 but the last two nights we've started at 7.30. She goes down by about 8.15 and two nights ago did 8 hours straight! Last night two feeds but didn't wake up to 8.30am!! I was awake worrying!
She wants to do 12 hour nights and I need to have her up, fed and dressed by 8.15 to do the nursery run so I've been moving bedtime forward. I was worried she would wake more but still only two or one feed a night. We did do the early bedtime for the first time on a Friday just in case the night was horrendous then dh could help out the next day. But she slept.
I've been finding she was so grumpy after 8pm that I just decided to do bed. If she naps after 6pm I would probably put her to bed a bit later.
I must confess though dd2 is a calm baby who sleeps. We would never have achieved this so early on with dd1.