@Render,
Yes, there is a lot of research on "happiness set points."
That is, context can shift things one way or another but people tend to revert to approximately their happiness set point.
Random Google result for "happiness set point," there is a lot more. Especially, look into Daniel Gilbert.
http://www.biopsychiatry.com/happiness/
It's not something that is written in stone, more of a predisposition -- inertia will get you there but if you're aware of it there are things you can do about it.