if i combine a hive, it's usually 2 weak hives that would have difficulty making it through winter. i'll pinch out the sorriest of the two queens and let the other one have it. imo, the advantages of combining are more bees now will definitely help collect stores for the winter, you don't have to worry about wax moths getting into a dead out, and you get to save that comb and the bees don't have to make it next spring. it wouldn't make much sense to combine two weak hives with two strong hives, because you lose two hives this way, but combining two weak ones, you only lose one. then in the spring you can split and have two colonies again. just a thought.