this is very a interesting discussion and i want to thank allen for explaining his observations and his thoughts behind them.   i think it makes good sense from the standpoint of using double deeps.

here's some perspective from one who uses a single deep along with one or two mediums for brood.

as winter wanes and spring waxes, the bees begin raising new brood to replace the long lived winter bees.  they will use their stores to accomplish this, along with what ever early flows present themselves.

i overwinter with an medium of empty drawn comb on the bottom.  a deep containing the cluster and some stores is next, and there's a medium of honey on top.  i popped the lid on my twelve hives last week, and at found them at this time to still have about one half medium of honey on average in the top supers.

what appears to be happening is that the bees are moving the honey down from the top medium into the deep for brooding.
 
in a few weeks there will be cycles of brood emerging and colony population will double and more in time for the early flows.  at this time the bottom medium will be brought up to the top.  an attempt is made to 'checkerboard' or mix in honey frames with empty comb.  this gives the bees all the room they need for brooding and nectar storage.  (additional mediums are then placed on top as needed for catching the main flow).

we are still having frosty mornings when the bottom box is brought up, but the bees have already moved down away from the top cover into the deep, and no harm seems to be done.

after the main flow and the summer harvest, a medium of empty comb is put back to the bottom.  this helps to cool the hive in our hot summers here, and give the bees a place to store summer pollen in anticipation of the fall brood up.

i credit walter wright for coming up with this.  it turns out to be a very bee friendly manipulation.  there is measurably less swarming, and measurably better honey production.

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