Much longer than 20 years I believe. Did you know that OA is critical to peristaltic action in humans? Look it up I try to balance my OAV use with drone removal too. I cannot bring myself to use Amitraz as an alternate.
Around me the fear of "the gas" has a large following so many other "chemicals" are used locally. This will level the genetic playing field I would think. I'm looking for, hoping for drones that are resistant to Varroa. This will affect the ability of the Varroa life cycle to reproduce at high rates, a la Asian honey bees. It would be nice if the "boys" contributed a little more to colony success.