There are two kinds of bizobjs. Ones that actually operate on the data, and a lighter weight bizobj that simply loads data called cDelogical, located in the cUtils class library.

I would use a single cDelogical object to load all the data for my comboboxes. You could use more than one, but really the only thing they are doing is opening a collection of views or tables to give your controls a datasource to map to. In a form where there are alot of controls and containers, the lighter weight you can make it the better off you are.