A change in temperament
Ageing is a desired transformation process in some teas, especially those belonging to the post-fermented dark tea variety. When stored correctly, the leaves will continue their post-fermenting during storage. As a result the leaves will gradually gain mellowness, while they loose sharpness and freshness.
In the case of Anhua Dark Tea, the traditional 48 hours pile-fermentation leaves a lot of room for ageing, while also making newly processed tea immediately drinkable and enjoyable. Newly produced Anhua Dark Tea is a finished product with a big ageing potential. Other teas may require a period of storage, until they can be truly enjoyed.
A big misconception, in my mind, is the idea that ageing makes a tea intrinsically better. Ageing cannot improve the quality of the leaves it is made of. It will slowly change a tea’s temperament, not its nature. It is therefore a question of personal preferences, rather than one of absolute superiority.
Not a quality criterion
I personally like to drink older tea later in the day, and when the weather is getting cold. I also very much enjoy the crispness of younger tea. Sometimes this is just what I want. The leaves are somewhat closer to their original state and it reminds me of the mountain they come from.
Aged tea is more expensive, because of its scarcity. I sometimes joke that great aged tea is hard to find, because the good stuff gets enjoyed first. I think there is some truth to that. The older the tea, the more difficult it gets to evaluate its exact age: it sometimes gets repackaged, broken into portions, changes ownership, etc.
Nevertheless, aged tea can be a real treat. I would just advise not to get obsessed with a tea’s age statement. If it procures delicate and mellow sensations, while at the same time letting you feel it was made with great material, everything is looking good!