Kleptos are fun, found it pretty effective with a pair, one keep the owners occupied while the other steal, then they switch.
One problem is that some days they don't want to steal three objects, perhaps because I stole to late the day before? You often have to return many days to get the item you want, have a strong feeling that the sims prefer to steal smaller objects before large furniture. Price doesn't mater much; just as well steal a laptop as a flower. And they have to steal the items on a table before taking the table.
Best advice is to search out places with little clutter, many rich sims has loads of clutter in their rooms making if less economical than a middle class house with little clutter.