The empirics of identity: Over what timescale does self-concept develop?

There is little more slippery than who we think we are. It is mixed up with what we do, what we want to do, who we like to think we are, who others think we are, who we think others want us to think we are, and dozens of other equally slippery concepts. But we emit words about ourselves, and those statements — however removed from the truth — are evidence. For one, their changes over time they can give insight into the development of self-concept. Let’s say that you just had a health scare and quit fast food. How long do you have to have been saying “I’ve been eating healthy” before you start saying “I eat healthy”? A month? Three? A few years? How does that time change with topic, age, sex, and personality? Having stabilized, what is the effect of a relapse in each of these cases? Are people who switch more quickly to “I eat healthy” more or less prone to sustained hypocracy — hysteresis — after a lapse into old bad eating habits? And, on the subject of relapse, how do statements about self-concept feed back into behavior; All else being equal, do ex-smokers who “are quitting” relapse more or less than those who “don’t smoke”? What about those who “don’t smoke” against those who “don’t smoke anymore”; does including the regretted-past make it more or less likely to return? With the right data — large longitudinal corpora of self-statements and creative/ambitious experimental design — these may become empirical questions.