Crown of thorns has a very small root system, only repot if you can see the roots are near the bottom of the pot. It tolerates the transplant better than you will - getting poked!
Mr Ponytail likes a pot twice as wide as the diameter of the bulb - so a 6" bulb should be in a 12" pot at least 10-12" deep. Keep the top 1/2 - 2/3 exposed.

Sometimes, if they don't quite need repotting yet, I scratch off some of the top soil, add a long acting fertilizer and a little new potting soil, and they are hap for another year. Just did that to my Texas ponytail before I left.

Sue

PS I brought home an orphaned orchid to rescue!