Christmas cactus may live for 25 years or more, and being slightly rootbound is actually conducive to blooming. If yours isn’t flowering or once did and has stopped, if it is top heavy, if roots are trailing out the bottom and there's no loose soil left in the planter -- just a solid root mass that can easily be pulled out of the pot in one piece -- repotting in a container just a wee bit larger than the original size may perk it up. Follow with a feeding, using a succulent soil mix with food included or supplementing with water-soluble fertilizer. I hope this helps. They like less water right before blooming - November or December.
Never had one of those, just the annuals and perennials. Sorry
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