My 4 month old daughter only goes down for her "long sleep" between about 10 - 10.45pm. Anything before that is just a nap and she wakes up after 40 mins or so. When she goes down for the night she'll usually wake once at about 2am, then sleep until 6-7am.
I don't really mind as I just go to bed immediately when she goes down, but sometimes I really crave an early night!
Most people I know seem to put their babies down at about 7.30pm, but if I was to do that (and she stayed asleep!), my daughter would be ready to start the day at 3.30am LOL