@philstalder she doesn't go according to the plant's needs, just according to what she wants to do. So she kills a lot of stuff, but if the plant's care req's jive with her care style then it'll grow like crazy. I know she had two more Chamaelobivia cacti planted in this pot. The other two rotted, but boy is this one happy! Also, it's a question of longevity. She's had this one at least 6 or 8 yrs.
@sunlovin yes, she has it at the edge of her patio, midway between a tree and a hibiscus bush. I think it only gets a few hours of late morning/midday direct sun, and other than that it's bright shade and reflected sun.