I can't remember exactly when we stopped swaddling our now 5 year old twins but we did it for a very long time. I had the swaddle sacks but eventually bought two Miracle Blankets in the natural cotton fabric. Best investment ever! If it was warm in the house, I would swaddle them in just their diapers. Eventually one of my boys would wiggle out of the Miracle Blanket every night (we called him Little Houdini LOL!). Then we used the sleep sacks which leaves their arms free.
Both of my boys are very sound sleepers to this day. I'd do whatever it took to encourage them to sleep. For their sanity and mine! Like another poster, I've strapped them into their car seats. My Little Houdini would occasionally get swaddled AND strapped in the car seat to prevent an escape attempt. We'd joke that he was our hostage at the insane asylum. (Which was basically true for our house with twin newborns!)
My advice... listen to your baby. If he's swaddled and sleeping through the night, he's doing just fine. If he was hot or uncomfortable, he'd wake up in the swaddle. If you think he's ready, try it without it. If he wakes up all night, he's not ready. Make sense? And if he's getting too big for his swaddle, you could even cut up an old twin sheet and swaddle him (I've done it!).
Good luck!