I think there are still bonded warehouses for whiskey in Scotland. The point is that they are under strict security to ensure nothing "disappears", and no duty has to be paid until the product actually leaves the warehouse. Some years ago I knew someone who had once supervised the digging up and analysis of the brick floor of a whiskey bonded warehouse ,to see if they could detect alcohol in the brick from a leak. The contents are checked by the excise regularly and there is an allowable loss during storage by evaporation, but the loss there had been much more than that and they were trying to determine where it had gone (!!??)