all babies are different but usually really little babies prefer to be swaddled because it makes them feel secure and warm - as they were in the womb.
I swaddled my DD untill 7-8mths. They say it becomes dangerous when they start to roll, so most stop then. Howeer my dd only slept while swaddled and couldnt roll they way i wrapped her! We moved to a sleeping bag when she was just to big to wrap around 9mths old.
We r trying out the wombies for bub #2.