Ken, If they are seedlings, it is best if you can keep them growing throughout their first winter. Of course this is different for anyone growing them in a climate where they are kept outside all year.
Most of the adeniums have an obligate dormancy period, but the obesum does not necessarily. If I can keep mine in leaf all winter, that is great. Sometimes they retain leaves, but do not put on new growth. If they do dormant, then this is meant to be. That is the way I look at it now.
Rick