So many of these anti-depressants and other meds used for off label purposes are so 'new' ....there really aren't many longterm researched results.
You bring up a very good question! I hope you get good feedback to this thread, as I've wondered this myself.....

As we age, our chemistry make-up, metabolism, hormones, etc do change even without meds, so in lieu of that I believe our personalities change slowly over time as we 'mature' and become more expierenced in handling situations life throws our way..... we can become 'bitter ol grouches' if we allow our hardships to take over......but medications certainly DO alter our dopamine receptors.......
We'll see what others have to say.....