I leave mine outside in the summer, sometimes watering if its been dry(these guys can take a lot of water in the summer outside in a clay pot).  Bring it in during winter, I'm around the 45 degree north latitude midwest USA.  Water sparingly in winter.  They could probably go all winter with no water.  I'd transplant that one into a large clay pot.  Use clay as this allows the soil to dry completely.  These guys grow at 10,000 plus feet, so they can actually survive light frosts.  They have cactus soil at the wally mart store.

Had a huge one at my moms that somehow died.  Believe my parents went on vacation and my brother over watered it.  I bought one foot long one ten years ago, now have four small-medium sized ones, and had that large one die, plus another 2-3 cuttings that didn't make it.  I believe I took these cuttings too late in the season and they rotted.