It certainly does change...
Just opened a bottle of Johnnie Walker Red Label I got from a cellar clear out after the death of an old lady. It certainly dates from the 1960's.It's totally unlike any JW I've ever drunk: much darker, with a pronounced smoky nose and taste, and a hint of oxidization. Interesting, but definitely not my cup of tea. It's reminiscent of a wine that's gone well past its best but is still drinkable. Pity it was only JW red - a good malt would have been far more interesting.