It's great that you like these blends as they are, as they're a bit different than they were, even a few years ago, much less 40 or 50 years ago.
We often talk about cellaring before a blend gets taken off the market, but what's becoming more apparent is to cellar something you like before it's maker decides to alter it. Tins are filled with something that's not the same blend all over the market, whether it's Rattray's or now Solani Silver, or Wessex Campaign Dark flake, components are getting subbed out. Why is anyone's guess, but changes have been widely noticed. Not all change is bad. But it is unpredictable when a blend that one particularly likes will disappear, even though it's tin says it's still there.