Lastly, I've coined the term perennial consistency to mean being consistent with the past and future of the API.
I chose the adjective perennial over others such as "perpetual" or "persistent" because perpetual implies the API will never change, which is impractical; persistent implies that developers should obstinately refuse to change the API even if there's a need to, which is not right; perennial means the API structure should stay the same for a long time, but not forever.
To understand why perennial consistency is important, we must first understand what happens when we introduce a breaking (backward-incompatible) change to our API.
