Double Black uses the 12 year old as a base and then they add younger western isles whiskies to give it more complexity. Hence no age statement.
That was Christopher Hitchens view on Black Label: beware of moving onto expensive whiskies, as you may find yourself somewhere where it's not available. Unlike JW Black. As a (ex) world business traveller, I get that.
It is pretty consistent, which is not always the case with blends. When they're doing a batch there's literally hundreds of barrels all piped up going into the run of bottles. Certainly, JW Red is not consistent. The apple taste is not always there, sometimes it's like treacle, but if you use it as it's meant to be, as a mixer, it does work even when the taste profile isn't as advertised. But never drink neat.
As you probably know, Winston Churchill was also a JW drinker, Red as it happens. But it was a different, better quality blend back in the day. That you could drink neat.
Famous Grouse is probably the best cost effective blend out there. Definitely worth checking out, especially the cask finishings. Stanley Kubrik use to drink it.