Going back to what Sue Eckert said, sanctions are not just about saying, if x, then y, that if I put in place a sanction, that's going to create a change in behaviour. It's also saying to the world, we collectively disagree with these policies, and to show that in the most tangible way we are going to target whisky. It may not actually create the change in opinion, but it starts a norm of everybody saying, this is unacceptable and here's proof it's unacceptable.
You are right, there is no guarantee that 10 years from now we're going to look back and say it was those sanctions that made the difference. We never just apply sanctions. It's a panoply of efforts, diplomatic missions, the six-party talks, and so on. There is no way to tease out the actual effect of the sanctions.