Re: I'm convinced that OAV is a cure-all for mites.
I am in the same area as johno. I am coming out of my second winter using OAV as my sole means of mite control. 1st year I was 16/16 until I starved a nuc. This winter I am 23/26, two were nucs that got robbed out and not mite related. The hive that died was the classic "my bees absconded" so I suspect mites although there was no brood and no frass. I treated almost every weekend August through October with a follow up in December. I'll take those numbers any day.
Thankfully, the bees are smarter than I am. They are doing well, in spite of my efforts to help them.