It would be handy to know in what period the twice refers to and whether the restriction is based on the effects on the workers or the Queen (safe to say both are affected with each treatment?). I've always assumed it was just once a year and so have been reluctant to treat swarms with OA during the summer so that I can use it during the winter instead. They stay in the garden until after the Autumn treatment when I put them in the apiary with the others, but it would be handy if I could move them straight to the apiary.