Could you be looking at the wrong thing? The current generation of workers won't make it to winter, what you need to watch is the size of the brood. It might even be that you could do well to tap the surplus workers into a super of empty frames overnight, remove it with them still in it in the wee small hours and euthanase them, leaving the brood box safe and crewed. The reason for this is you don't need a lot of redundant mouths noshing the winter reserves for the next month while bringing nothing in, depends on the state of your honey flow too. It's the effect of the early spring bringing the flows in early, leaving us with nothing coming in and a month or more before they really settle. As we can't be certain of the same next year, perhaps it's time to do artificially what comes naturally: look on it as an extension to what they do with the drones anyway. Perhaps that should be the trigger for when to do it, they bounce the drones, they get culled themselves too.
