Re: Not treating or no Queen for winter, better route??
What is the temperature there? Have they kicked out the drones yet? Are your hives honey-bound/does she have room to lay?
With the break in brood caused by winter, your mite population will go down drastically.
In my first year opinion (book learning, no experience), the queen may have shut down laying for the winter. This will get rid of a huge amount of mites. Treating at this point is kind of redundant. You said that both queens quit laying at the same time and you have been treating them for different amounts of time. The queens might have thinned down a bit (no need to lay for winter) and it could be that she is hiding under other bees (keeping warm) so, they would be hard to spot.
If you think anything organic is good for you, go drink some organic solvents.
geek, learning how to be a beek