I guess I should summarize. If feel you need to split them more three week before the honey flow and you want to maximize the yeild and you don't mind spending the money on a queen, then buy a queen so they don't have to lose another brood cycle they could have reared. If you can wait until about two weeks or less before the flow then I would just let them raise their own. It will save money and actually free up more bees for the harvest who don't have to care for brood.