I think it is safe to say that the vast majority of human groups or cultures have some sort of god concept. That seems to be more or less universal. Maybe you can say it is an element of human nature. Modern scientists seem to spend considerable energy discovering exactly what constitutes human nature. Some even say there is no such thing as human nature. Either way, the concept of god seems to differ quite dramatically from place to place, even from time to time. My conclusion is that God is only eternal in the sense that just about all of humanity recognizes that there is such a thing as god. God did not create the universe, our prehistoric forefathers created God. That is why God is different from culture to culture. To this day scientists dedicate their lives to figuring out where the universe came from and still arguing vigorously about it. Theologians and lay people insist God created it without a shred of evidence other than the words of the Bible written thousands of years ago. Since the existence of some kind of god concept is the one thing that unites us all, figuring out exactly what that means has become really important. Obviously, we do not have written accounts of what the earliest humans were thinking, but some of the artifacts they left behind give us some clues that they were in fact thinking about it. Our knowledge about God took a major step forward with the invention of writing. The oldest writings about our version of God were limited to a vocabulary of about 3,000 words. Even with this limitation, the ancient writers did a remarkable job explaining who God is. The vigorous debate about what it means still going on today is not due to their writing abilities, but to the limited understanding modern theologians have of ancient culture.
Therefore, God is not a physical thing. You can make a statuette or a painting representing God, but it is not God. God is the invisible force that ties us together. There are many things that tear us apart, but the bond that keeps us together is God. Being in communion with God, caring for one another, is what protects us and provides for us. Therefore, the expression that God is good all the time and all the time God is good has way more meaning than many people realize. For many Christians, saying it is simply a ritual that identifies you as belonging to the Christian community, but it goes far beyond that. What is important to know is that humans are fundamentally good and take care of one another in community. Because humans created God, God is good. God is community.