The age of whisky is determine from the date it is bottled minus the date it is distilled. After putting it in the bottle, the "age" does not increase. In other words, if your JW Red has been sitting on the shelf for 20 years, it is not really 20 years old. As for blended whiskies, it is compose of many single malts. The age is determine by the age of the youngest whisky component.
The other bad news is that the price of blended scotch whiskies does not appreciate that much compare to single malt whiskies.