I reckon 24hrs, or at most 48hrs, in the tank should be enough to see if the treatment works - in my experience, it should have worked by that stage. If not, then the fish might need to be in the tank for another couple of days if you wanted to try adding more, with a water change. If you wanted to try one of the medications, then it's usually about a fortnight.
Obviously, you don't want to stress/shock the fish with vast temperature changes from the pond to the tank temperature, so hopefully others with pond experience can advise on that and any other issues to consider when transferring pond fish into tanks and back into ponds during winter.