Thanks for having this discussion Guy's very helpful. I find these two statements to be very important relating to what I've been playing with.

>With such high mite levels, we now understand that there were likely virus
issues in those highly-infested hives, which can have a substantial effect
upon honey production, due to early death of foragers.  Thus, it may be
difficult to separate out the effect of viruses from that of the amount of
drones.<

As I have all colonies with unrestricted drone rearing.
Some colonies that I use for honey production will show DWV during early drone rearing with only drones effected which disappears around the beginning of the main honey flow in my location. Then in the fall as would be expected reappear affecting the workers. Depending on the level of damage too drones in the spring seems to be an indicator as to what the level of damage workers will take in the fall. With the drones taking the hit I see the workers being able to build a fairly strong work force to take advantage of the nectar flow.
 
>As you say, though, these colonies are not moved to continuous flows, and
thus may not provide varroa with as much continuous brood in which large
mite populations can develop.<

I sometimes wonder if the mites can to a degree settle into an annual cycle more in tune to the bees in a stationary situation.

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