I own two Adenium plants. One has shiny leaves, the other has matte leaves with a somewhat velvety texture to their undersides. I originally thought that the one with the matte leaves was Adenium obesum, and the one with shiny leaves was something else, possibly Adenium arabicum. Now, after some confusing reading, I think that it is the other way around. (More or less--they could each be hybrids of one or both, with maybe a third species thrown into the mix. At this point I'm ready to say "whatever." )
Anyway, I've had them for a few years, and I've been a bit rough on them. One winter, I kept them in a warm but not very sunny spot, and they lost their leaves until spring. The next winter I tried them under fluorescent lights in my cool-ish basement, and they held on to their leaves until I got a little lax in my watering. This past winter I put them on a sunny windowsill in my kitchen where I could keep an eye on them, and tried my best to water more regularly. They never lost all of their leaves, but they started to look a little straggly, with browning or yellowing of the leaf edges, by February, when I pruned them.
Despite my less-than-optimum care, they always bounced back, and looked attractive during the spring and summer. Neither one has ever put out more than a flower or two, and they seem to do so in alternate years. Last year, it was the (putative) A. arabicum's turn, this year the A. obesum (supposedly) is blooming.
My plan for this winter is to switch them into plastic pots. Although Adeniums do have a semi-deciduous nature, I think my leaf loss problems were mostly due to erratic watering. Plastic pots, which can be more water-retentive than clay, might help with that. I do think that the kitchen in the sun is better than the basement under lights. Not only is the basement a bit cooler than they might prefer, but I don't go down there daily, and I might not notice that they are too dry until too late.