Its been discussed many times in the forum. No flow, no wax, no extra honey. Queen excluders are a negative factor and work better for specific things, but not so well if routinely slapped on every time we super. Sometimes colonys become complacent. I think the topbar guys are learnig first hand that a colony expands so far and sorta stops unless they super and challenge the bees to fill them. You can bait them up when its warm with some brood, but even that doesn't always work. When I experience something like this, I think it's time to look at the queen. If she's not causing the population to grow and occupy the super, if her offspring aren't racing back and forth loaded with nectar and pollen, then she's not the anchor you want in that colony. Lazy queens make lazy colonys. It happens. When it does, it's nice to have a couple nucs around with a pinch hitter ready to go. When I have a colony that is booming, or catch a swarm that is going gangbusters with no sign of slowing down.... thats the one I pull a frame of eggs from for the nuc to make a queen for me. The added benefit is, she'll have the nuc busting at the seams in short order, and you can rotate sealed brood and keep strengthening your producing colonys. If I'm not nervouse about em swarming, there aren't enough bees in there.