Are Love and Affection Transient?

Thinking about all these nonsense at the time of recession may be the symptoms of insanity, but let it be; after all we are human first.
The last few weeks were quite wearisome for me because of million of stupid reasons, but managed to have an interesting discussion on this topic with a friend. Are love and affection transient? Science claims that emotions are triggered by a molecule in the body which starts vanishing with a certain period of time. So what is the fact?

• The love and affection towards the parents, especially in the urban Indian culture starts receding once the person establishes his / her own family. May be because I am staying 3000 Kms away from them, I might be biased in the observation, but baring some exceptions, this relation is assumed to be most vital in human’s life. So what's the reason of weakening of this relationship, is it a kind of transiency effect or just an overshadowing of the old relationship with the newer one?
• The Plato theory talks about the initial structure human body as union of man and woman. The body was later cut into two pieces; hence both of them are always in pursuit of finding out the other part. Now even if they are able to find it at least in case of love marriages (let’s forget the arranged marriages for the time being as I strongly feel that it is nothing but one more bigger compromise in the human’s life) the differences start cropping up in their lives after a certain span of time.

So to conclude this, definitely the transiency effect exists in the humans and according to me, to mitigate this, it is important to preserve the basic human values like innocency and honesty and shed the individuality. The Bollywood says this in its own style -“Avoid using brain where you can handle the situation with heart.”