I believe that in specific environments where certain needs are not being met that a persons morality will change. Do you expect a starving person not to steal food? Depression and stress can also lead a person to take heed in poor advice and question their values, and morals. I refuse to believe that decisions I once made that hurt myself means I have loss in my morality moving forward in the rest of my life.
Whilst an over-riding personal opinion is possible, your general morals are a reflection on what your family and the greater society around you deems acceptable/unacceptable. Therefore, as society and culture gradually changes over time, so does its morals, even if imperceptible at the time. There can also been marked shifts in morality over a relatively short period of time, often occurring during times of persecution.
That's the very important word that this question hinges on.
The basis of morality is empathy and well-being. It is founded in the human interactions, and that basis will never change.
Our opinion of morality may change, our moral systems we use to evaluate the world may change, but the basis of it will not since it is intrinsically connected to how humans act when affecting each other.