How much is the freshness of love?

According to a study by the scientists in the United States, the freshness of the true love is 18 ~ 30 months. Study points out, love is actually made of the brain chemical dopamine, phenethylamine and oxytocin, similar to a chemical cocktail, but it is not such as first jumps over Chen yue sweet, but in the long run, the body will be in this material to produce antibodies, the failure of two years or so, men and women after break up, or let love become a habit.
Thought, love is made up of glistening silver inapproachable jiang jing, private luxury cars, homes, or romantic, crazy, no IQ behavior and is accompanied by a racing heartbeat, breathing disorders, vomiting and dizziness phenomenon, but I didn't think the love is a chemical element of these odd plus freshness. Science gradually in the quantitative digital our love, I really don't know after marriage proposal enlightenment is wrote: "the number of units for dopamine, phenethylamine units, oxytocin several units of a female (male) company... "However, I think, well, love freshness and shelf life supposed to be different, vegetable freshness will rot, the need to throw away. The so-called let love become a habit, should be a transition from freshness to the shelf life, love is the freshness of 18 ~ 30 months, shelf life should be a different length. Some people grow old together forever, some people cast had to break up