I have had these for about 6 years now. They withstand dry conditions-I bought it at a cactus show-but seem to much prefer average moisture. Just last weekend I found the latin name and did a web search, finding this thread amongst other information. There is a lot of inconsistent data out there. The species name is also reported as cordatum. Along with Pregnant Onion, it is also called Desert onion, Healing onion, Sea onion or False sea onion. There are reports of its use as an anti-burn agent, like Aloe. The sap is, I suspect, where it gets its genus name, 'bird's milk'.
Mine flowers annually, and has produced a whole bunch of offspring. After flowering, they seem to tip to one side, perhaps from the weight of the long stalk. Quite an amazing plant.