Thoughts on which hives get robbed

I have 10 hives in my backyard. I have two hives which did not have queens. I put frames with eggs in and they both finally ended up making new queens. Once I saw the queen cells, I stopped putting in frames with open brood and eggs. It took my putting several frames of eggs in over a month or so to get new queens started. One of the hives had a laying worker and the other had a non-laying queen which I did not find for a while so they were not starting queens until the pinched the non-laying queen. Even though the nectar flow stopped quite a while ago, the robbing did not start until they both had new young queens, but they were not laying yet. I have always heard that queenless hives tend to get robbed when the nectar flow slows. I am wondering if it is not that queenless hives get robbed, but that hives without open brood get robbed. The nectar flow slowed here in Cincinnati quite a while ago and both those hives were weak, but not robbed. Perhaps the pheromones from the open brood deter the robbers more than the queen pheromones. Has anyone else experience this? I would like to hear your thoughts on it. Jim