They actually prefer to be kept rather rootbound, so perhaps it would be best to leave it in its current pot. They are a pretty low maintenance plant all around. As you've had it for 4 years you obviously have been doing a good job with its care. Overwatering is one thing they don't tolerate well; they also like to have a winter rest in a cooler room. Now is the time they generally come into bloom, and they bloom for quite a long while. Enjoy your plant!