According to the American Academy of Pediatrics:
The age for weaning off the wrapping varies from baby to baby. Many people think they should stop swaddling after a few weeks, when their baby starts resisting it. But, actually, this is when swaddling becomes the most valuable.
To decide if your infant no longer needs to be wrapped, try this: After she reaches 2 to 3 months of age, swaddle her with one arm out. If she gets fussier, continue wrapping (with both arms in) for a few more weeks. However, if she still sleeps well with one arm out, she probably doesn’t need swaddling any more.
Most babies are ready to be weaned off wrapping by 3 to 4 months of age, although some continue to need the wrapping to help them sleep up to 9 months of age.