With my first, my daughter, it was instant. I did have a loss, and a period of infertility before she was born, as well as a scare during pg, so it was just so precious to actually Have her here. The bonding was pretty instant, after the placenta was out. But it still takes a while to get used to the idea that you are a mum, I cuddled/fed her for a while straight after, but then I was ready for a shower! lol. And at 5am the next morning when she woke me up, I remember thinking 'oh yeah, I have a baby now'!
With my son it took a bit longer, I don't know if it was because he was a boy (I had no idea what to do with a boy!), or because I was away from him for a couple of hours after birth (complications), or because he was my second child. I really had to speak to him, call him by his name, pray over him while breastfeeding, make time for just the two of us, and the bonding came in nicely! I kept thinking of 'the baby' as a chore, get the baby settled so I can do x,y,z etc. I think the bonding took about a week, but it's also a constant, growing thing!