Seven Generations is a term in some cultures that indicates long-term thinking.
I think Evan is drawing from an Indigenous / First Nations understanding. It means that you need to think about the impacts of your decisions for the next 7 generations.
But 7 generations is also found in the Judeo-Christian tradition. In the Bible, seven generations is a stand-in for eternity or a really long time. And in India, you get married for 7 lifetimes (basically forever).