From spring to summer, the brood nest will move down. As the colony expands, bees build comb downwards, and new brood is by preference at the bottom of combs, pollen above, nectar and honey above that.
In autumn and winter, they start at the bottom and eat their way to the top.
At the end of the winter when stores are at their lowest, what's remaining is right at the top, in the warmest place for the coldest time of the year.
Then it repeats.
Of course in practice it's not as neat and tidy as that, but in general that's how it works.
