I have not been into whisky all that long, and my experience is greatly limited. But I have been a serious wine fan for many years, and there are many simularities. No two vintages from the same house are the same. They may be a similar style, but always different.
There are too many variables to distill a reproducable single malt, I think. Sure, there are "house styles" that are the result of the shape of the stills, and the various methods of handling malting, washback, etc. But it is impossible to buy exactly the same ageing casks every year from the same sources. Some sherry casks from Spain, if I recall, are no longer available at any price. And a very large part of the final product is dependent upon the casks used in ageing. So the single malts will vary from year to year and batch to batch, and cask to cask. In addition, no one truly knows the long term effect of ageing to the point of being able (either blending or time-wise) to accurately predict what that 1985 malt will taste like in
2005.
Cutty Sark, J&B, Chivas Regal, Johnny Walker, Famous Grouse are all consistent for the most part. I prefer taking my chances with single malts. Much more interesting, and, yes, there is a risk. Alas, if I find a fantastic bottle of SM, and I don't go immediately buy a case before the batch is all gone, I'll never taste that whisky again. Mac 12 is different every year (if they make it), because it was all made 10 or more years ago under conditions that can't be exactly reproduced again in today's stocks, and I've seen reviews of Mac 10/12 vary from average to fantastic depending on the batch.