Every company should define a set of values when it first opens. These values are in place to help you and your team grow.
For example, when 5 different people are trying to make decisions based on their own personal values, it will be nearly impossible to cohesively run an organization. But with a framework for how to behave and make decisions, those 5 people can be aligned.
Now, why would you change your core values over time? Simply put, you outgrow them.
Take the time as a team to revisit your core values every now and then. It is a major time investment, but it will be well worth it.