A great automated test suite is one that allows you to change the internal architecture of the system in any way, with confidence that the system still behaves the same towards its clients after the change is committed. The more the system changes over time, the more the test proves its value over and over again. The older a great test gets, the more value it delivers in facilitating change. So a great test gets better with age. Very much like a great wine.
A great architecture is one that makes the system do what it needs to do and makes it easy and cheap to add many new features. Unfortunately there are always trade offs in the direction of change that an architecture allows. Ultimately the architecture of a product, with some very limited exceptions, becomes the limiting factor in change. In this respect its like a great cheese, it will age well for the first while, but eventually degenerate and rot.