The importance of reserves
Having enough to eat during the winter and early spring is an important topic for Bees. Bees store their food source because they do not hibernate during the cold months and must have enough food stores to last until they can get back to foraging when the weather turns.
It is important that there is a variety of honey within the hive, summer honey as well as honey stored from late autumn because honeys from different seasons and plants will store at different hardness. Ivy honey stores, gathered in the Autumn and Winter, is very hard and would be impossible to digest if not mixed with softer honeys.
I saw more activity from my hives in January than I have in March, this is due to a mix of very cold days with milder very wet days neither of which are good days for foraging. So that means the Bees are continuing to eat last years honey until they can get out again. This honey from last year must be very good quality if they are going to survive. I can't expect the Bees to live on sugar water, because there is no nutritional value in this supposed honey replacer, so I don't give them any at all.
My own rule of thumb is about one third of the total stores gathered by the end of August could be harvested from the hive after a very good summer of fine weather. If the summer was very wet, then less or no honey would be harvested. This way I am not interfering with the only source of food and nutrition available. There will be some good weeks of foraging weather in the Autumn and this will boost their stores before the colder weather settles in.
We have all been, at one time or another, without any reserves of cash or cache and it is a frightening situation, so don't overtax your bees by taking more than they can afford to spare.