Every year, my wife's folks send us a 5-pound block of 5 year old cheddar from Gibbsville Cheeses in Wisconsin. This is really fine stuff, with a lot of flavor and a crumbly texture. For some reason, they sent us two blocks last year. We went through one of them, but the other ended up sitting in the back of the fridge, to be routinely noticed during cleanings and then forgotten about. When we received this year's block of cheese (fortunately, just one) we figured we'd best unwrap last year's and either start eating or throw it away. Turns out that the year in our fridge was quite salutory - it went from really good to world-class. Along with the strong cheddar flavor, it's developed a hint of a musky character. There's much complexity and great length of flavor. There's a tiny bit of a white mold on a couple of the surfaces, but that's the only "flaw". It's as good or better than any cheddar I've had.
We'll see if this year's cheese develops as well as that one.
"An expert is a man who has made all the mistakes which can be made, in a very narrow field" - Niels Bohr