It probably just depends on the baby. My middle baby was very rarely off the boob 24/7 until I stopped nursing when I got pregnant again (high risk.. wasn't an option to keep nursing) He was a little over a year anyway.
My youngest use to eat for longer but with a bigger space in between. He was my first baby to sleep through the night at about the 2 month mark. It was awesome. :D He was a real easy baby.