Hi:  I know both George and Jim and respect each for their knowledge of
bees.  However, having conducted research in Maryland, where George
resides, and in Washington, where Jim resides, I think some of the apparent
contradiction has to do with the geographical areas, types of beekeeping,
bee forage, etc.
 
As in Washington, in Montana we have at least one commercial beekeeper who
has double queened about 2000 hives every year for at least 15-20 years,
possibly longer.  He has impressive production records.
 
Western Washington and Eastern Maryland are much alike in that each area
has lots of small side-line beekeepers.  More importantly, the main nectar
flows are finished by early (no later than mid-) summer.  In both areas,
beekeepers tend to pull honey supers, then feed honey.  They also
intentionally shut down queens early in the season.  With mild winters, the
problem is that the bees need a lot of surplus honey to cover all of those
mild months when they can move about, even fly, but find only a subsistence
or lower food resource.
 
Eastern Washington and eastern Montana are different.  We have large
migratory beekeeping operations.  2,000 hives is "a small" operation.  Some
go to 14,000 or more.  The main nectar flows start as early as May and can
continue on an off and on basis right through August.
 
Some of our beekeepers shut down their queens (but usually a month or two
later than the folks on the coasts).  Others want every bee that they can
get to catch the mid-summer flows.  In a good year, these operations
produce over 100 pounds surplus, often 150 pounds (and I have seen and
verified large runs of apiaries that can harvest over 200 pounds) with an
occassional hive cranky out as much as 500 pounds (and yes, I have weighed
them).  However, I haven't seen these monster hives much since the mites
popped on the scene.
 
One thing we don't do in Montana is feed in summer or fall - only in the
spring.
 
Our challenge is to get strong colonies going fast for a relatively short
season, after which we put them to bed for the winter or haul them to the
west coast.
 
Double queens get the populations going fast (which can be an advantage for
colonies coming out of a long, cold Montana winter, or struggling to
recover from the rigors of migratory pollination.  Slow build rates, and
you miss the critical nectar flows.
 
Like Jim, we estimate a queen loss of 30-50% as not being uncommon in these
commercial operations (and yes, some of our industry folks were dispute
that number) but both Jim as a Washington state inspector and ourselves
having tested colonies over landscape scales have looked into thousands of
colonies.  Queens can and do fail more often than generally thought.  They
also tend to be lost about the time the queen excluders are dropped on or
as the main nectar flows really gets going (based on our MT studies).
 
In my opinion, the advantage of that second queen is as an insurance policy
during the early part of the season.  Our commercial beekeeper actually
lets the two fight it out mid-summer so that he goes into the winter with a
single queen cluster (otherwise we tend to get two clumps of bees in the
hive).
 
However, in eastern Maryland (or eastern Washington) you don't need (and
may not want) large populations of bees mid-summer or during the winter.
 
Here, we still argue whether a large population is more likely to survive a
Montana winter (and as such justify the extra honey needed).  Again, I like
strong colonies.  Our records show a much more consistent and predicatable
performance record from strong, over-wintering colonies (but that probably
reflects the vagaries of keeping bees in this geographical area).  With the
advent of the mites, this may be even more important - since most losses
occur during the fall, winter, and early spring.
 
Cheers  Jerry