When to transition out of swaddle?

kmpage28

I am wondering what others have done/when transitioning their LO's out of a swaddle at night.  I am torn about whether my LO is ready to start the transition...When I put her to bed, I swaddle her and she thrashes/moves around quite a bit until finally settling down...Is this just because she is settling or because the swaddle is getting to be too much for her...She kind of bucks around a bit then settles...I have been considering trying to leave one arm out as a test but am unsure...she will be 13 weeks on Thursday...