Ace, if u would clarify, so all understand . what u mean by bee's not having a good fall flow ?
I will say what is typical in the north. I don't yet have bees here in FL... too occupied renovating my house.
Bees prepare for winter. They gather nectar all summer long for two purposes. One is to raise winter bees and the other is to overwinter. Overwintering includes raising spring bees. The actual amount of honey needed to make it through the cold months is only a fraction of what is required to make the spring bees. Most northern states have a heavy flow, usually goldenrod and aster or knot weed. Some say this is not good to overwinter on because it can cause dysentery. I took honey only in the fall from the top boxes so more of the spring and summer honey was left for the bees if they did not consume it all making winter bees.
You can play roulette by taking more in the fall then you should and feed like heck in the spring. If it weren't for the fluctuation in weather it would work great. So as the bees intended leave an excess in the fall to cover the unknown.
From what I have read the south is quite different. They may or may not have a fall flow. Their flows in general are not as plentiful. They have much longer periods of flying weather (which consumes more honey) but they also have nectar available for a longer period of time and they can be fed more easily. That being said, granular sugar is not a good feed. They can't take it fast enough to store it. If you can, feeding syrup is the answer. If they can't store the feed they can't raise brood. If they can't raise brood it is a downward spiral to perishing. The south also does not have a reprieve from SHB and wax moth like the north does. So in general managing a hive in the south is quite different then the north. A beekeeper must lean the location his bees are in. You can get advice on the internet but helpful advice comes from your neighbor who is raising bees.