I do not drink expensive blended whisky too often, saving my dollars for single malts.
However I've had the chance over the years to taste some luxury blends. One is Johnnie Walker Gold Label, another (just twice or so) the JW Blue, once the 25 year old Cutty Sark. I noticed a trademark taste in all these. They had what I call the "old books" taste. This is a flavour or smell of old paper and leather, sometimes mixed with flowers. "Old roses" is another term used in whisky terminology. This was married invariably to a smoky (peaty) background with a marine saline edge.
This must be an old style of blended whisky and as I say a few brands still offer that taste.
Recently a friend brought over a circa 1970 bottle of Grand Macnish that had long been in the family bar. The label was partly worn off. The name Macnish was still clearly legible and the words 70 proof (i.e., 80 proof in American terms, this was bought evidently in duty free and still bore the now defunct Sykes designation of ABV). I could not tell however what the age expression was.
We opened it and the taste was rich, malty (almost sweet), smoky and redolent of old books and old flowers. It was quite similar to the current Johnnie Walker Gold Label. It evidently had old whiskies in it, probably some 15-20 year old whiskies and possibly some that were yet older, thus going back probably to 1950 distillations or earlier. A rich dram of whisky, complex and satisfying. Few drams offer that palate today. It can only come from a certain style of blending and the use of some old malts which offer that specific palate. My guess is some were Islays aged by the seaside or Campbeltown whiskies from distilleries no longer in operation. (Campbeltown offered a zingy saline character - Springbank's whiskies still do although in a subtle way).
Some old rye whiskeys also get to that old roses/old books palate (e.g., some ORVW 13 year old rye does, also BMH 18 year old rye, and others). I mean, straight rye and malt whisky will always be different but I note a certain connection in some samples of the aged articles of both. Whereas bourbon, good as it can be at older ages, doesn't attain in my experience this dimension of flavour. Probably it did in the past.
Gary