Neat plant Dave. I find the variation between plants within the species fascinating. Another interesting difference is your plant does not have a pink mid strip on any of the petals while mine has the stripe on some but not all of the petals...go figure.
I don't know about your plant, but this is one of my slower growing mams. It took a minor forever for the pups to flower.
A lot of cacti grow but do not gain the amount of height you would expect Doug because they concertina at the base like a set of bellows folding, hence the denser spination just above the offsets on the plant.
You know these cacti are really nice. Probably not hard to keep, they more than likely don't bark at night and you don't have to worry to much about anyone grabbing them up to look a them, well maybe only once. Beautiful flowers there Dave.
Main advantage, unlike tomato plants in the greenhouse, is you don't have to water them twice a day. Also if you have got automatic window openers you can go away for two weeks in high summer without needing to water them. Not many other plants are that care free.