I could be wrong, but I don't think doak is attributing the losses to varroa. What you are referring to is ourbreeding the mites, which is a different topic.
I believe doak is talking about queens
dying faster than in the past, not necessarily the bees dying due to varroa, then the colony failing. But it could be that.
why requeen a good queen just because she's a year or two old ? Then eventually you're selecting for queens that are only viable for a season. I replace my queens when their pattern starts to fail or they have poor characteristics, not because they are old.
There are a number of advantages to requeening every year or every other year, as opposed to waiting for the queen to fail naturally. If you requeen every year, you are ensuring that genetic diversity is being put back into the hive. If you got one new hygienic hive, requeening your other hives will make use of the drones that are flying around carrying that hygienic behavior. If you wait and requeen as needed, genetic diversity only occurs every three years or so. You also ensure that the hives that make it through the winter get their genes passed on. If you have one hive that has a great characteristic of being resistant to varroa, requeening every year ensures that you can spread that characteristic among the rest of your hives faster. The downside, of course, is that you can spread poor characteristics just as fast.
Also, by requeening before
you see problems, you are in a sense getting rid of problems before they occur. You get the chance to requeen before the queen fails, preventing the hive from dwindling in numbers more than it would have to.
There is also an article (actually a few) out about queens that are produced after the summer solstice (June 20th). Those queens seem to produce better through the fall, and overwinter at a greater percentage, or so the theory goes. Requeening every year allows the colonies to overwinter better, theoretically.
Last, I would just like to point out that if you are requeening whenever you see the pattern start to fail, not only are you behind the curve in fixing a hive problem, but you are also essentially requeening an old queen. So while you arn't choosing queens directly based on age, in a sense you really are. Older queens tend to have their pattern fail. Also, even if you requeen every year or every other year, that doesn't mean that you can't requeen every time a poor characteristic is shown either.
That of course isn't mentioning the fact that it's much easier to just routinely change out queens. Most people change their oil every 3 months or 3,000 miles. Some times the oil is still good after 3,000 miles, and could make it another 3,000 miles. But most people just do these regular maintenance issues as preventative to problems.