I'll say 6 - 8 weeks. I remember DD3 being 5 weeks when she started sleeping from about 8 - 5 every night.
I think she was around 4 months when she started night feeds again. I think it was 'wonder week/month'.

The struggle for me was maintaining those cluster feeds. Trying to deal with other kids & dinner made it harder, but if she got in her full 2 - 3 hours cluster feeding she slept much better.
ETA: DD also fed 2 hourly through the day, so she got all she needed through the day for that night sleep IYKWIM.