Old grain whisky from a good cask can be really superb, usually with a fair meatiness too them. You've picked out a really good one with that Carsebridge (I assume it's the recent Duncan Taylor bottling) - it has a rich oakiness and velvety quality to it, fruity (raisins) and dry. I didn't take notes, but here's notes from Whiskyfun:
Very waxy, on vanilla, rum, raisins and burnt cake. Not extremely complex but very satisfying and totally flawless. Hints of fructose, fresh pineapple that add some extra-balance to it. Superb!
It's a shame you don't intend to open it, but I guess at over £70 you're not going to buy two.