Forgive me, but I am not entirely sure what you are getting at.
I would say the definition of any given is word is determined by an involuntary consensus between the population or culture that uses it. Whatever most people interpret it as, is what it should mean, which is why the definition of words needs to be updated in dictionaries at times.
Your comment about the definition inspired me to check google myself in order to ensure I was not misusing the word, and I found that I was not. So, I am unsure of where you are finding this definition of content that you shared with me, but I am unable to find it, and you are the first I have known to understand it to mean what you claimed it means.
The number one definition for content is "a state of peaceful happiness." This is exactly what most people want, and that's why I used the word, whether I remembered the exact definition or not. There is no mention of a time frame to suggest that content is short lived whilst happiness is long term, so I can only assume you added that part to the definition on your own. Hence why I thought you were redefining the word.