I'll preface this statement with my qualifications in the area. I have a Ph.D in analytical chemistry with a minor in biochemistry.
        That said, it's my understanding that bee's have invertase in their stomach which inverts sucrose (table sugar) to fructose and glucose.  Inverted sugar is sweeter than sucrose.  Hence, it is impossible for bees to store the syrup that I feed them as sucrose syrup.  The bee's may store the syrup that I feed them, but it will be modified/inverted and sweeter than the syrup that I feed them.
        With that in mind, I have no hesitation to continue to feed the bees syrup as long as they take it.  
                                Yours, Dr. Dave